Well ... let's try to explain again

I saw tutorials on how to create a website layout with GIMP !
They design the whole page in GIMP !
And then they write the html code !
WHAT I DON'T UNDERSTAND :
- How do they slice the whole image (layout) and create the html code with the images !
I'm thinking (but I know this is stupid) - that GIMP has some options like EXPORT TO HTML and then it slice automat all the images and renders a page !
I'm trying to do this because I have a script and I want to create a nice template for it !
And then for others sites just to use the template created but with slightly modifications !
I hope I was more clear in the paragraph above
