CD’s

The subject of this post is about CD’s. No, I’m not taking about the CD’s that we listen to, when I’m writing of CD’s, I’m speaking of the Certificate of Deposit-type CD.
Honestly, what is the purpose of a CD? Supposedly, the money is supposed to “mature” for some time before the user is allowed to take it out and use it. I believe my mom put a CD in my bank account for me sometime in October–$500. She was telling me all the great perks to having a CD in my bank account, so without even researching about it, I eagerly agreed to it. Now, one month before “mauration” of my CD, I was looking at it, and I honestly wonder what the purpose of setting aside $500 for non-use for a few months was for if the money amount isn’t going to increase much. I was looking at my CD deposit today,  and to my dismay, I only had $505.
I don’t think I’m going to go for anymore CD’s. It’s really not worth it-or is it?
I think my best bet would be to get a job–to become employed. That way, I can pay for flute lessons (without having dear mother transfer money to my bank account) and other needed/wanted items by myself.