chromebook is basically a cloud terminal. You have the abilty to save some material locally, but the presumption is that most of your stuff is in the google cloud
A linux kernal with Chrome browser running on top. Some basic file management functionality and power management. Fast boots especially from sleep.
If you use the google platform (as I do, completely) then your whole life is delivered through chrome browser. Docs, drive, picasa images, google music, etc etc. You dont need a chrome book to do this as the google stuff is platform independent, but for some sleek and tidy samsung hardware why not?