HyperCard is kind of a database. It's 'kind of' a database in the same way that
LotusNotes is - pretty free-form, not relational, and often document-based. It is predicated on the idea of 'stacks' of cards chained together, with actions and events associated with each. Cards also contain simple graphics and hypertext.
HyperCard was developed by the great Bill Atkinson for Apple in the late '80s and runs on the Mac's 'Classic' OS (i.e. OS 9 and earlier). HyperTalk?, the scripting language used to chain cards and stacks together, is a simple, natural scripting language not dissimilar to the today's AppleScript?.
Again like LotusNotes, one could argue that HyperCard contributed to the development of the world wide web in that it made extensive use of hypertext and allowed 'stacks' of cards to be linked together. Apple's management never really supported HyperCard much, and it got shifted around a lot during various re-organisations, with the product officially at the end of its life in March 2004 (having languished for some time prior to that). A great shame. It did give the world Myst though.
Read more at Wikipedia