In order to own bitcoins you need a wallet. To get started, you generate a private key through that wallet. Your private key is just a very large random number and your bitcoin address is calculated from it. By having a private key, it means that you can sign a message proving that you own the address without having to reveal its key. Thus, in bitcoin you broadcast transactions by "locking" funds on addresses that can only be spent if someone owns their private keys.

Example of a wallet import format private key:

Example of an address (that one is called "Legacy"):

To answer that, yes. It is like code. Anyone having that 256-bit number called "private key" is able to spend your money. That's why you should keep it secret.