General Maintenance Task List: these are task lists that are used for general maintenance tasks. As a result, they can be used for both equipment and functional location. They are not specific to any technical object. General maintenance tasks allow you to define and manage a sequence of maintenance tasks and use them for scheduling.
Functional Location Task List: this list is assigned to a specific functional location. Consequently, you can use a functional task list to centrally define and manage maintenance tasks for your functional location.
More information in the SAP PM Task List tutorial.