HyperTalk is the programming language that came with Apple Computer's HyperCard. It was created by Dan Winkler. HyperTalk scripts are not standalone, to be executed they must be part of a HyperCard stack.
HyperTalk was designed to be as English-like as possible so that it would be easy for non-programmer to modify and create their own programs.
HyperCard came with several resources for learning HyperCard, one of which was a full Script Language Guide. There was also a HyperTalk Reference stack bundled with HyperCard, of which there exists a PDF. However, perhaps the most complete reference to HyperTalk is the book series "HyperTalk: The Book". Initially published with a focus on HyperTalk 2.0, a later edition was released to cover HyperTalk 2.2. As well as including a description of all the language terms in the language, the book highlights some bugs and limits of the language. (It's completeness is perhaps due to the fact that one of the co-authors of the book was the original designer of the HyperTalk language).
Several modern implementations of HyperTalk are available, with varying degrees of compatibility. The language used in LiveCode is estimated to be around 70-80% compatible with HyperCard, but there are some major differences. OpenXION aims for compatibility, but this has only been largely achieved for non-graphical use due to the fact the OpenXION is command line only.
Several attempts have been made to translate HyperTalk to other programming languages, and are listed on the Open Source xTalk Interpreter Archive. However none have achieved 100% compatibility.