HyperTalk scripts within a HyperCard stack usually involved reading data in from text-field on a card, manipulating the data, and then returning some answer into another text-field. The language could also change cards in the stack, do "special effects", play sound, or all sorts of other nifty things. HyperTalk and HyperScript were so powerful they could be used to develop entire games (for instance, there was a Cosmic Osmo game that was basically a massive HyperCard stack on a CD. I used HyperTalk at one point to make a simple RPG, which functioned rather well).
HyperTalk has virtually disappeared after they heyday of the Mac Classic.