I'm no expert but here's my explanation..
When you mine you are helping verify transactions on the network. Basically every time you send a cryptocurrency it needs to be verified by a certain amount of miners before it goes through. Once you verify a certain amount of transactions (usually a huge amount) you will get a block, and in each block you get coins.
New altcoins are unpredictable. They could gain value or just die off so deciding whether or not to mine is up to you. My best advice would be to research a lot before you start using resources.
I'd also recommend mining in a pool because they find blocks much faster. You almost always get more when you mine in a pool as opposed to mining solo unless you have some crazy set up where it doesn't take forever to mine a block.