Why can the same wallet store so many different tokens?
ERC-20 defines a standard set of interfaces, such as totalSupply, balanceOf, transfer, approve, and transferFrom.
Don't send tokens to the contract address of the token itself. Most of these contracts don't have a way to transfer tokens out, so they're basically impossible to recover once sent.
ERC-20 tokens run on Ethereum, and transfers require $ETH to pay for gas. Currently: 2357.88.
Drop a 1 if you learned something. If you still have questions, ask in the comments.