NetLogo is a multi-agent programmable modeling environment. It is free to use. There is an online version that works well for running existing models and there is a downloadable version that is required for these tutorials. Before you dive into NetLogo, get familiar with the cast of characters in this programming environment.
Turtles: The objects that you control with your programming. Each turtle has a position, heading, color and pen. You can add more specialized traits and properties.
Patches: The piece of the world in which the turtles live. Like turtles, patches can execute NetLogo commands, and they can act on turtles and patches. Patches are arranged in a grid, with each patch corresponding to a square in the Graphics area.
Observer: The observer "looks down" on the turtles and patches from a bird's eye perspective. The observer can create new turtles, and it can monitor the activity of the existing turtles and patches.