k your slices are saved along with the html code in a folder that you specify(preferably the same folder that you will save as your root folder in your html editor).
You can optimize each slice of your image seperatly,choosing the best compression to keep integrity but low file size.
It is quite straighfoward but sounds technical i know.Photoshop or image ready(depending on which app you use) to slice creates the html code for you and will save all the alignment and such and this code will piece all your sliced image to gether on your web page.
It really is easy, all that
ppl really need to worry about slices are that they are saved at the best compression and low file size.
there stacks of tutes on slices out there best of just searching for them in google or something. [righton]

hope this helps