What is CORS (Cross Origin Resource Sharing)?
Cross Origin Resource Sharing is something that is declared by the w3c on communication between different domains. By CORS, communications between the same domain will be allowed to users and the communications that are cross-originated will be restricted to a few techniques. We can see this when we are talking to APIs mostly. The REST call may give us an error. This is because the server and the client sides are on different domains and the communication between them are restricted by CORS rules.
If you want to learn more,please do a google search. you can find a lot of resources related to CORS and their importance.
The Spring has given a nice explanation and that can accessed with following URL.
Importance of CORS
The importance of the CORS implementation comes with the security aspects. It blocks the calls made by unknown domains and keeps the paths open only to the known domains. So the security is ensured despite the attacking requests.