Copyright is used to protect artistic and literary creations from being misused by anyone and so that no one can claim it to be theirs.
Almost all the big music labels have a copyright on their songs, and can easily issue a complaint if used illegally.
Nowadays students make short films to submit to different film festivals and without any knowledge about copyright issues; they end up using different music or songs from various places.
Therefore, before using songs or music, you should do thorough research about the music industry and the copyright music and legal terms.
Professional or independent filmmakers are well aware of the fact but most students who make amateur films or are beginners are not very much aware of it.
However, there is a piece of good news for you, if you are a student who wants to make films and music to it.
Many labels with copyright music are easy on students, as they expect the films to be non-profitable if they use their music and do not do any harm or slap any legal notice. So before using any music go through the legal terms and conditions of that company.
Also when you submit your film to festivals many festivals will ask for a clearance letter or acceptance letter about the music you have used in your film, so be careful with that, mostly big or renowned festivals ask for such things. If you are submitting your film to local film festivals, they are easy to persuade.