These terms are used a lot in the context of web security to distinguish between different types of requests or resources.
Same-Origin is when two web pages have the same origin if the protocol, port (if specified), and host are the same for both pages.
https://ondrejsevcik.com
request tohttps://ondrejsevcik.com
Same-Site is a more relaxed version of same-origin. It allows pages to interact if they're from the same site, which means they have the same registered domain.
https://sub.ondrejsevcik.com
request tohttps://ondrejsevcik.com
Cross-Site refers to situations where interactions happen between different sites.
https://ondrejsevcik.com
request tohttps://github.com
Hope this helps.