Just typing "about:" will show general and version information. It's kind of short for about firefox :)
It's a firefox easter egg. Try it.
New easter egg.
Shows a blank page.
Shows Firefox configuration.
Shows information about Firefox cache. You can even browse the files in the cache.
Shows the list of contributors who helped develop Firefox.
Displays a list of plugins installed on Firefox
Information about the particular build of Firefox.
Shows home page of Firefox with Google search bar
Shows troubleshooting information
Show the Mozilla Logo
Shows memory usage of Firefox