From the Soar webpage (ai.eecs.umich.edu/soar/):
Soar is a general cognitive architecture for developing systems that exhibit intelligent behavior.
Soar is a programming language used for AI which was developed some 20 odd years ago by researcers at Carnegie Mellon University. It is a rule based language with puts it in the same category as languages like prolog. Soar was originally written in LISP, and later rewritten in C. Soar also has fundamental ties to Tcl. The basic unit of code in Soar is a rule, but in Soar they're referred to as productions. For this reason, Soar productions start with sp. Here is the cannonical hello world program:
sp {hello-world
(state <s> ^type state)
-->
(write |Hello, World!|)
(halt)}
As a language, Soar is very specifically for creating agents that perform some sort of behavior within the confines of a given world. It can be used to solve most of the classic computing problems as well, but its primary applications today are in military simulation, and game bots.
Soar's editor of choice is the Java-based VisualSoar.