There are a few special URLs, which begin with about.
You can type into the Location Bar:
about
about:about
about:addons
about:buildconfig
about:cache
about:compartments
about:config
about:crashes
about:credits
about:downloads
about:healthreport
about:home
about:license
about:logo
about:memory
about:mozilla
about:newtab
about:permissions
about:plugins
about:preferences
about:privatebrowsing
about:rights
about:robots
about:sessionrestore
about:startpage
about:support
about:sync-log
about:sync-progress
about:sync-tabs
about:telemetry
