Newbie Question, Whats a cross section?

Support Basics & Interface
1

What is a cross section. I was looking at a character modeling tutorial and on the first step, it said to make a cross section. How do i make this?
Oh and this is the tutorial.
http://neenjatech.org/projects/character/body/page1.html

2

If you used a bandsaw to cut a person in half at the hips, the bloody part would be the cross section. If you cut a boat in half from the bow to the stern and then look at one of the halves, looking at the inside of the newly ventilated hull from off to the side, that would be the cross section.

%<

3

OK but how do I make it?

4

Make a plane in top view, subdivide, and shape.