Are tongues for today?  Are they unknown or known tongues and what is the meaning of angelic tongues?  Can you explain 1 Corinthians 14 to me; this is the chapter that my relatives say proves that speaking in tongues is for today.

No. They went out of use with the sign gifts. The sign gifts were miraculous gifts given during the apostolic age (before the completion of the New Testament) so that those to whom the apostles preached would know that the word they spoke was really from God. When the New Testament was completed and direct revelation was no longer given, there was no longer any need for the sign gifts. Notice these characteristics about the sign gifts.

1. The signs were given for the purpose of "confirming the word" (Mark 16:20And they went forth, and preached every where, the Lord working with them, and confirming the word with signs following. Amen.
   See All...). This means to prove that the words they spoke with their mouths were from God.
2. The signs included taking up serpents and drinking deadly poisons (Mark 16:17-18 [17] And these signs shall follow them that believe; In my name shall they cast out devils; they shall speak with new tongues; [18] They shall take up serpents; and if they drink any deadly thing, it shall not hurt them; they shall lay hands on the sick, and they shall recover.
   See All...). If we are supposed to do one, then evidently we are supposed to do the others.
3. The signs were given especially for the Jews (1 Corinthians 1:22For the Jews require a sign, and the Greeks seek after wisdom:
   See All...). God often deals with the Jewish people through signs beginning with Moses (Exodus 3-4).
4. The signs were given (especially tongues) in order to convince the lost. "Wherefore tongues are for a sign, not to them that believe, but to them that believe not" (1 Corinthians 14:22Wherefore tongues are for a sign, not to them that believe, but to them that believe not: but prophesying serveth not for them that believe not, but for them which believe.
   See All...). They were never given for the pleasure or spiritual experience of the saved. This verse says that they are not for those that believe.
5. Although tongues were still allowed at the time of the writing of 1 Corinthians (14:39), they were on their way out. We see this in the great number of regulations Paul puts on the speaking in tongues and in his emphasis on the lesser importance of tongues (14:1-9). He also clearly says that tongues "shall cease" (1 Corinthians 13:8Charity never faileth: but whether there be prophecies, they shall fail; whether there be tongues, they shall cease; whether there be knowledge, it shall vanish away.
   See All...).
6. Tongues took the path of apostolic healing through the instrumentation of man. Christ healed all that came to Him (Matthew 9:35And Jesus went about all the cities and villages, teaching in their synagogues, and preaching the gospel of the kingdom, and healing every sickness and every disease among the people.
   See All...). The early apostles did the same (Acts 5:16There came also a multitude out of the cities round about unto Jerusalem, bringing sick folks, and them which were vexed with unclean spirits: and they were healed every one.
   See All...). Yet, before the New Testament was completed, Paul could not heal himself (2 Corinthians 12:7-9 [7] And lest I should be exalted above measure through the abundance of the revelations, there was given to me a thorn in the flesh, the messenger of Satan to buffet me, lest I should be exalted above measure. [8] For this thing I besought the Lord thrice, that it might depart from me. [9] And he said unto me, My grace is sufficient for thee: for my strength is made perfect in weakness. Most gladly therefore will I rather glory in my infirmities, that the power of Christ may rest upon me.
   See All...) or his co-worker, Trophimus (2 Timothy 4:20Erastus abode at Corinth: but Trophimus have I left at Miletum sick.
   See All...). He kept Doctor Luke with him (2 Timothy 4:11Only Luke is with me. Take Mark, and bring him with thee: for he is profitable to me for the ministry.
   See All...) and told Timothy to take a prescription of medicine (1 Timothy 5:23Drink no longer water, but use a little wine for thy stomach's sake and thine often infirmities.
   See All...). God still heals through prayer (see Philippians 2:25-27
   See All...), but He does it directly and not through the touch of a man.

They are unknown in that they are languages no one present knows. When tongues were spoken on the day of Pentecost, every man heard the word in his own language (Acts 2:8And how hear we every man in our own tongue, wherein we were born?
See All...). This is not angelic language. Paul only uses "the tongue of angels" as a contrast. [Even if I spoke in the language of angels, that would do no one any good if they could not understand me.] He was not defining unknown tongues an angelic language.

1. Tongues were already unimportant in the service of Christ by about 60AD.
2. The most carnal church Paul wrote to (see 1 Corinthians 3:1-4 [1] And I, brethren, could not speak unto you as unto spiritual, but as unto carnal, even as unto babes in Christ. [2] I have fed you with milk, and not with meat: for hitherto ye were not able to bear it, neither yet now are ye able. [3] For ye are yet carnal: for whereas there is among you envying, and strife, and divisions, are ye not carnal, and walk as men? [4] For while one saith, I am of Paul; and another, I am of Apollos; are ye not carnal?
   See All...) was caught up in tongues-speaking and gave way too much emphasis to it.
3. No speaking of tongues should be done unless the tongues are interpreted (v.27-28).
4. No more than three should ever speak in tongues in a church service (v.27).
5. Only one should ever speak in tongues a one time (v.27). That's what "by course" means--in order, one after the other.
6. Those who truly speak in Spirit-given tongues can speak if they want or refrain from speaking if they want (v.32). God-given tongues is not some uncontrollable urge that comes over someone. It is a gift that they can use when they want just like preaching.
7. Women are not to speak in tongues in a church service (v.34).
8. Truly spiritual people will agree that these restrictions are necessary (v.37).
9. Paul clearly told the Corinthians that tongues were going to “cease” (13:8). When would they cease? Tongues were a form of divine revelation; thus, the importance of interpretation (14:5). They would cease when God’s perfect revelation was completed—that which is in part is replaced by that which is perfect (13:10). God’s perfect revelation is found in His completed Bible and no new revelation is needed (Revelation 22:18For I testify unto every man that heareth the words of the prophecy of this book, If any man shall add unto these things, God shall add unto him the plagues that are written in this book:
   See All...).

I do not think that many churches follow the rules set down by Paul for the speaking in tongues. Does the church your relatives go to follow all these rules? If not, then they are not following God's plan.

You see, Paul was kindly regulating tongues to a minority role in the church at Corinth so that it could die out gracefully when it was no longer needed. It was no longer needed when the New Testament was completed.