Closure Library: a JS library containing a bunch of useful stuff. Closure Compiler: A compiler that takes Javascript as input and produces Javascript as output

Closure Library: a JS library containing a bunch of useful stuff. Closure Compiler: A compiler that takes Javascript as input and produces Javascript as output. Removes dead code, does various optimizations, and usually beats other minifiers by a small but significant margin. Closure Templates: a templating system that generates Java or Javascript code. Handy if you want to generate a bunch of HTML from templates in Javascript, and you don't want to write all that by hand.