hasn't coinbase been hacked several times? once was this year?
So don't use it for storage, only for exchanging
so is bitcoin stored on my actual wallet ?
If bitcoin is a file, the blockchain is a disk, the wallet address (representing the private key) is a directory, and the wallet is a file manager. Just imagine where your bitcoins are actually stored.
If you can't understand this simple analogy, you might feel like you've lost all your files if your WinExplorer suddenly crashed.