A pool is a container for a process in a diagram. A lane is a division of a pool (think of swimlanes in a swimming pool). You can use lanes to group elements of a pool that are functionally related. Typically, a lane contains all the tasks assigned to an actor.
When you create a new diagram it contains one pool, which contains one lane. You can add other lanes to the pool, and you can add other pools.
For a pool, you can configure the following: