Welcome to GOY. Simple explanation in this link. http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookPLANTANATII.html
Is this your homework? What course are you studying?

Exam question alert, I think!

If so, I recommend that you actually learn and understand the info, Dazmo, rather than just cutting and pasting. I use one aspect or other practically every day as a Master Gardener, and it will be of at least some use to anyone who has a profession related to natural science.

I am not really even clear about the wording of the question.

Different layers? As in what root structure/stem etc?
The link fro Scotsgran has some very good images and is nicely laid out. Is that what you mean?

I've only just found this question - thank heavens, Seaburngirl, that it's not clear to you either - I just thought 'what layers, what does that mean...' If its an exam question, I've failed already, lol

I assumed the question meant layers in the leaf structure. Glad I'm not doing any exams any more.

but a good question would state 'tissue' layers and then stem/root/leaf.