There are two different types of Tasks; 1) manual tasks and 2) automatic (watcher-triggered) tasks.
Manual tasks are created by CoolPlanetOS users. Using the task template, you can manually create a task, assign it to colleagues, and have CoolPlanetOS notify them of it and record it for them in the list of tasks.
Watcher-based tasks are CoolPlanetOS generated records of each incidence of an event which happened as a result of the conditions of a watcher "rule" being met. To illustrate, if I create a watcher to monitor if a specific air compressor exceeds a specific ton/hour target, and that rule is met once per hour, then I will have 24 events per day, each one is a record of this condition having been met. If I wish to be personally notified about this, then, in the watcher, I will have specified myself as the "default assignee". Once per hour, when the condition of the rule is met, an event record is created and stored with a parent "task", assigned to me, will be created.