If you use Org mode extensively, you may end up with enough TODO items that it starts to make sense to prioritize them. Prioritizing can be done by placing a priority cookie into the headline of a TODO item, like this
*** TODO [#A] Write letter to Sam Fortune
Org mode supports three priorities: ‘A’, ‘B’, and ‘C’. ‘A’ is the highest, ‘B’ the default if none is given. Priorities make a difference only in the agenda.