A summary task is a description of a set of activities, which are work packages. A work package is a group of activities for which work is estimated, scheduled, monitored, and controlled. A work package defines work at the lowest level for which cost and duration can be estimated and managed. For example:
Constructing a shed is a summary task, while laying the foundation, constructing a frame, and building a roof are all work packages within the summary task.
Installing a purchasing software module is a summary task, while loading the software, porting over existing purchasing data, and testing the new software are all work packages within the summary task.
Training employees in a new safety program is a summary task, while writing the training materials, training the trainers, and conducting training classes are all work packages within the summary task.
In each of the preceding examples, when all of the work packages are complete, the summary task is also accomplished.