Official description from http://windows.microsoft.com/en-US/windows7/products/features/sticky-notes :
Already as necessary as pencils and paper clips, Sticky Notes just got more useful. In Windows 7, you can format a note’s text, change its color with a click, and speedily resize, collapse, and flip through notes.
If you've got a Tablet PC or a touchscreen, Windows 7 Sticky Notes support pen and touch input, too—you can even switch between different input methods within the space of a single note. Sticky Notes is available only in the Home Premium, Professional, Ultimate, and Enterprise editions of Windows 7.