How to solve this problem of "! [rejected] master -> master (fetch first)"

How to solve this problem of "! [rejected] master -> master (fetch first)"

First Do this ...

git fetch origin master
git merge  master

Then, do this ...

git fetch origin master:tmp
git rebase tmp
git push origin HEAD:master
git branch -D tmp

Now everything works well.

thank you so much it worked well !!

Thank you very much!

Thanks

Thanks so much

Can somebody please explain, why do we get this error? And how these above lines of code solves the issue!
ps-issue is resolved. Please someone explain.

Thanks a lot!

Thank you sir.

Thankyou so much!!!