What is "access-control-allow-origin:" in http request/response?

Hello Parnam,
Please check the below url:
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Access-Control-Allow-Origin

The Access-Control-Allow-Origin header indicates that whether the response from other origin can be shared with requesting source from the given origin. It is part of CORS. A web browser compares the Access-Control-Allow-Origin in response with the requesting website's origin and allow to access the response if they match.