Smalltalk is a programming language, though very often the term is used to indicate a programming environment for the language. Note that the t in Smalltalk is lowercase.

GNU Smalltalk implements the recognized ANSI standard for the Smalltalk language, which is ultimately a descendant of the Smalltalk-80 language developed at Xerox PARC. Much of the class library is identical to that of Smalltalk-80: they both have objects, classes, single inheritance, blocks, garbage collections, collections, streams, and many other bits. In addition to this, GNU Smalltalk provides other classes including networking and GUI programming.