Livecode extensions are written in Livecode Builder and come in two flavours; widgets and Libraries.
# Introducing LiveCode Builder
LiveCode 8, the upcoming release of the LiveCode HyperCard-like application development environment, introduces a new xTalk-like language for writing LiveCode extensions. It's called LiveCode Builder (or LCB). It shares much of the same syntax as the original LiveCode scripting language, but it's a compiled, strongly-typed language - peter-b.co.uk
Most of the public discussion about LiveCode Builder has revolved around using it to extend LiveCode — either by creating new widgets to display in the user interface, or by writing libraries that add new capabilities to the scripting language. However, one topic that *hasn't* been discussed much is the fact that you can write complete applications using only LCB, and compile and run them without using the main LiveCode engine at all.
Livecode Builder is a new dialect of LiveCode in which you are able to write things called extensions. An extension will (in the first instance) either be a library or a widget - livecode.com