The global TODO list contains all unfinished TODO items formatted and collected into a single place.
agenda-mode, so there are commands to examine and manipulate the TODO entries directly from that buffer (see Agenda commands).
org-todo-keywordsis selected. The r key in the agenda buffer regenerates it, and you can give a prefix argument to this command to change the selected TODO keyword, for example 3 r. If you often need a search for a specific keyword, define a custom command for it (see Agenda dispatcher).
Remote editing of TODO items means that you can change the state of a TODO entry with a single key press. The commands available in the TODO list are described in Agenda commands.
Normally the global TODO list simply shows all headlines with TODO keywords. This list can become very long. There are two ways to keep it more compact:
org-agenda-todo-ignore-with-dateto exclude such items from the global TODO list.
org-agenda-todo-list-sublevelsto get this behavior.