Copyright

From LentzWiki

Copyright is the fundamental, moral and implicit right of the original author of a work (be it a book, a song, or a computer program) to be recognised as the owner, and decide on its distribution. In its basic form, the owner retains full rights (all rights reserved).

You can also register (assert) your rights explicitly, for instance by getting a document timestamped at a post office, or by depositing a copy with a notary. This could make providing proof in case of a dispute easier. But, as noted above, your implicit have the rights anyway.

For computer software, Open Source provides a mechanism whereby the owner grants additional rights to distribute and use. Contrarily, traditional software licenses (often called EULA - End User License Agreement) further restrict what a user can do, above and beyond basic copyright law.