So, when I first started doing full stack development, I didn't have the knowledge about cores. That is a cross-origin. Basically, when you connect backend and frontend, and backend requests to your frontend, multiple requests can come. So, you have to optimize that which request from, like, this backend has to send a request to which frontend. So, this is done by cores. In Node.js, we have a package called cores. We put in the frontend URL in there, and then we can connect this. Basically, we use HTTPS protocols and etc., etc. to connect, basically, between protocols are used to, as backend server contacts into the frontend.
