Why we use different tags like div, section, header etc. when they have a similar function?

Answer 1

It's for make code more easier to read

Answer 2

In term of styling, they are the same. Semantically different.

Answer 3

Sharjeel Faiq hi,
Browser and search engine use their meanings.
These three ressources have common content, plus some stuff about search bot.

https://developer.mozilla.org/en-US/docs/Web/Guide/HTML/Using_HTML_sections_and_outlines

https://www.pluralsight.com/guides/semantic-html

https://www.semrush.com/blog/semantic-html5-guide/amp/