A "cross section" is typically used when analyzing data. It usually means data collected at point in time which someone surveys a particular group such as poor and wealthy and then this data is compared to find the differences between the 2 groups. The sample taken is referred to as the "cross section" if it statistically represents the groups at the time.

Your question should be 'What does 'cross section' mean?' and you asked this same question 10 days ago? Have you forgotten this already? Or did you not believe the answers you were given? Here is your question: http://classic.italki.com/discussion/110646 and here's the answer I gave you: A cross section has examples from all classes. 'Section' is a cut, and 'cross' means 'across'. Imagine you have a gateau made in layers, with cake, chocolate, cream, fruit and so on, one layer on top of the other. If you take a bit from the top, you'll only get what's on the top layer, won't you? But if you take a knife and across the cake, the slice you take out will have a sample of all the layers that the cake is made up of. That's what a 'cross section' is.