What is the use of <!DOCTYPE> tag?

Question

Brief it.

Answer 1

See these

https://en.m.wikipedia.org/wiki/Document_type_declaration

https://stackoverflow.com/questions/414891/what-is-doctype

https://www.sololearn.com/discuss/172624/?ref=app
https://www.sololearn.com/discuss/254171/?ref=app
https://www.sololearn.com/discuss/1388028/?ref=app
https://www.sololearn.com/discuss/1899685/?ref=app
https://www.sololearn.com/discuss/470075/?ref=app
https://www.sololearn.com/discuss/895904/?ref=app
https://www.sololearn.com/discuss/1499896/?ref=app
https://www.sololearn.com/discuss/822818/?ref=app

Answer 2

It is the root of any html script and it is always there