Edit Keys displays your animation as a series of keys, displayed as boxes on a grid in the Key window.

(Edit Keys)This tool is available only in Dope Sheet mode, where it is active by default. The alternative Dope Sheet modes are Edit Ranges and Edit Time.
Edit Keys is useful for getting a global view of your animation because it displays animation timing for all tracks. Use this mode for key and range editing when you want to view your changes in the context of the total animation.
Use Edit Keys mode to:
To activate Edit Keys mode, do one of the following:
(Edit Ranges) mode is active, then on the Keys toolbar, click
(Edit Keys).To delete keys in Edit Keys mode:
Delete to delete the selected keys.