Tasks are executed by composites. Composites are important because they directly affect the flow control within your Behavior Tree.
Composites come in three forms at the time of writing this: Sequence, Selector, and Simple Parallel. Here's a description of each:
Sequence: This executes each node, returning success on the last node; however, if any node fails, it will immediately return failure and abort the rest of the leaves.
Selectors: This executes each node, returning success immediately and aborting the rest of the leaves. If a node returns failure, it continues to only return failure if the last child returns failure.
Simple Parallel: This executes one task and a subtree at the same time, which allows you to walk and allow another tree of decision making to be at the top of the walk task, for example.
Tasks are usually the last node in the change to be called as they contain the code that would affect the AI actions directly. We will make...