Paper wallet is just a sheet of paper where your private and public keys are written down or printed out

This is just what you need to know (and obviously no one else should) to access your bitcoins on the network as well as send them using any decent software wallet that allows importing the keys. And as far as I know, any desktop wallet allows that. Bitcoins themselves are stored on the blockchain (and never leave it), so you access them using these keys by a Bitcoin address, which is basically a hashed public key itself