What is the error 401 402 403 404 405?

They're HTTP status codes. They are nothing but the errors in HTTP.

The error codes of 4xx are called client errors which are caused by some mistakes done my the user.

They error codes mean:

401 - Wrong Authentication

402 - Requires some Payments to be done

403 - Authentication required, no public access

404 - Web page does not exist/Required content not found

405 - Method of sending data is not allowed