Well, you can buy BTC or if you have altcoins just exchange them on BTC. You can start mine, but it's more difficult. I can recommend you some good and trusted sites where you can buy or make an exchange
There are a lot of posts in this topic at the forum and a lot of books.. even movies. Google and you'll find everything. And after you'll make your vision more clear and ask in the forums about things you don't understand
The main difference between altcoins and tokens lies in their structure. Altcoins are independent currencies with their separate blockchain, while tokens work on top of the blockchain, which facilitates the creation of decentralized applications.