What are uses of stylesheets?

Question

i have confused about html and css stylesheets could anyone explain ?

Answer 1

HTML is only the structure part.
For example, this part is my header and that part is a link and here a picture should be loaded.
CSS is all about the looks.
Positions,colors, borders,fonts and ...
PS:Some of these looks can be set using only html too but now days mostly CSS is used for all of it.

Answer 2

Very simply...

HTML says what to display.

CSS says how to display it.