Each task in the Projects application belongs to a Project or an Area. Tasks are grouped into Lists, according to when they should be done.
Some task details are displayed in the list:

Tasks can be created in the following ways:

Task details panel displays task fields and allows to edit most of them in-place:

It also has Comments and Recent Activity sections:

Besides in-place editing, tasks can be also modified through special Edit panel. Some operations can be applied to a number of tasks at once—see Tasks Bulk Operations.
Tasks have logging work functionality: estimates, logging work hours, etc.
Existing tasks can be Completed or Canceled. Tasks, created by mistake can be deleted.