What is the certificate's use?

I am really confused about what the certificate is used for and how can it be used. And is the certificate approved by organizations and companies?

I mean, it is meant to be proof that you completed the course. As far as I know, there are no companies that would just hire you because you had certificates of completion from some online courses. These are trying to produce something similar to a transcript for you. So it is just some tangible evidence that you did actually study this material.

Any serious company looking to hire will verify that you can do the work rather than just checking your credentials. It is possible there may be companies out there that would not let you interview unless you had some form of transcript proving you had studied this material. Then the certificate may come in handy. Otherwise it is more like a merit badge. Cheers!