What and where are the interpreter and compiler in HTML?

Answer 1

Compiler and Interpreter are used in Programming language to convert high level language C, C++, Java into low level language assembly/machine code.....
HTML is text markup language.........
Therefore, no need to use compiler or interpreter....
But, Browsers do contain something similar to interpreter ....
.

Answer 2

Probably here https://en.wikipedia.org/wiki/Gecko_(software)