An altcoin is a completely seperate currency, with its own blockchain, that isn't dependant on another blockchain, has it's own wallets etcetera.

Tokens are usually based/made upon another crypto currency. Take for example the ethereum protocol. There's tons of "tokens" which are on it. They use the same wallets as their parent currency, are (mostly) coded the same way, etc. (-- If Ethereum would stop functioning, so would all the tokens that are on their platform.)

You should see tokens as another currency inside the blockchain of another coin.

https://coinmarketcap.com/tokens/