See NetLogo overviews for an overview of NetLogo.
NetLogo is primarily an IDE for developing agent-based models. Here is how some of the important concepts map onto NetLogo concepts:
Environment = World
Mobile Agent = Turtle
Stationary Agent = Patch
For example, here's a screen shot of Sugarscape:
Most of our models instantiate the ABM Framework.
A brief description of this framework can be found in NetLogo Overview #2.