what is whitespace?

Question

I am learning html and one lesson was about how to use or create whitespace but I didn't understand it.

Answer 1

It is just, a space
Lemme put a whitespace between two quotations:
" "

Answer 2

" " ← Whitespace

Answer 3

Sometimes tabs and end of lines are considered whitespace.

"int
i
=
0
;" is identical to "int i=0;" to almost all compilers.

Answer 4

In summary, whitespace has anything other than a readable and "font-affected" character