A Bitcoin address is a unique identifier which allows you to receive Bitcoins. With PayPal you send funds to an email address, and similarly with Bitcoin you send funds to a Bitcoin address.
For example, this is one of our Bitcoin addresses: 1JArS6jzE3AJ9sZ3aFij1BmTcpFGgN86hA.
Please verify that you have copied the destination address exactly before sending Bitcoins to it. Bitcoin transactions are not reversible!