As its name implies, AppleScript is an Apple technology; a high-level (meaning accessible) programming language designed to give experienced users a bit more power in working with applications and the Mac OS.
Here are the most useful of my latest scripts for OS X (I'm not sure how they'd fare in OS 9 or Classic):
Adds a very handy Change Case command to the Script menu in AppleWorks 6 with options for UPPERCASE, lowercase, And Title Case conversions.
Prior to OS 10.3 "Panther" the Mac OS wasn't smart enough to keep individual user preferences for sound volume settings. This spiffy app takes up that role.
A dandy script for iTunes (Mac only version, of course) that does what its name suggests.
Another handy iTunes (Mac) script. Plays the selected track or playlist after the current track ends.