@yugexh_ said:
about api
I am using api key for an school investigatory project now I got my api key ,
so can I know the Rate Limits for that

API Request Limit
The limit should probably be a maximum of 40 per second / IP.
Here's what Travis Bell, the Administrator, said.
https://www.themoviedb.org/talk/66997ca6d3a5dbcf7c3a7994?page=1#669a84b510ab9ed1d367341a

The easiest way to help with your issue is it to introduce a small delay in between every requests so that you are issuing more than ~40 per second.
There are fancier designs where you can keep track of the number of requests in a second,
and then limit the number you execute within a threshold of sorts.
It's really up to you how you want to implement this.

Your second question.

and other main terms,

Hmm, your question is very broad.
I can suggest some links.
https://www.themoviedb.org/faq/account
https://www.themoviedb.org/faq/website
https://developer.themoviedb.org/docs/getting-started
https://developer.themoviedb.org/reference/intro/getting-started