Start pages are just like websites - but they're not hosted on the internet. They're built in the same way (With HTML and CSS, or other 'languages') and can have the same functionality and features, like animations, clocks, weather updates, newsfeeds, searches, embedded media etc.

Popular start pages: http://pastebin.com/nEq2KqSw

Previously submitted pages: http://imgur.com/a/j0NHf

Learn some basic HTML and CSS to build your own here: https://www.codecademy.com/courses/web-beginner-en-HZA3b/0/1?curriculum_id=50579fb998b470000202dc8b