Magic Words, or keywords, have special meaning in your Ubiquity commands. They are generally used as shortcuts to things relating to a command - for example if you've selected some text then the "this" keyword will be a shortcut to that text.
This page is a work in progress aimed at listing exiting keywords and their uses as well as storing a list of proposed new keywords.
this - current selection
here - geolocation-specific
me - geolocation, email address address - URL currently visiting