Hope you know some python.
AI Gym is a collection of mini world's for training bots/agents. The mini worlds are called environments. Some of them are really simple. But, there are some really complicated ones too like the starcraft one.
Also not all the environments are included with the base install. You'll need something along the lines of
pip install gym[all]gym[thingsHere] have different environments. There are some other pip installs
for box2d and py-atari and whatnot you will need.