What is the difference between a 1st level domain and a 2nd one? Indexing?

Question

Domain Name System

Under the 1st level, I mean a domain of this type "domain.ru", and under the 2nd "damain.sait.ru", I want to know how much the indexing difference in the browser will be

Answer 1

Wrong you mean.
ru is the first level, domain.ru is the second, and damain.sait.ru is the third.
And they differ only in level.

Answer 2

The browser does not index anything. This is what search engines do. There is no difference for SEO at all.