doctype html means

Answer 1

it is gives representation to the browser that it is a html 5 document.

Answer 2

@Maxel Varley wrote: << doctype means you are using html 5, if you dont add doctype mean you are using html 4.01. >>

Wrong... If no use of <!doctype>, browsers can not guess wich version is used, and would turn into a 'quircks mode' with older standard basics than Html4 (when there was mostly Netscape and IE as browser choice and they don't provide much compatibility between them ^^

Html4 have specific uggly <!doctype>s dedicated to each of its different flavours, and has been simplified for Html5, but not providing a <!doctype> declaration, will absolutly not turn implicitly your document to be parsed as Html4 specifications :P

https://developer.mozilla.org/en-US/docs/Quirks_Mode_and_Standards_Mode

https://hsivonen.fi/doctype/

Answer 3

DOCTYPE basically tells you what type of document are you about write..
like for XML DTD file we write
<!DOCTYPE note >

Answer 4

HTML Version