The Node Window is a workspace or desktop for compositing. This clip covers all the mouse and hot keys you use for navigating around and in that workspace and discusses how to add/delete/move nodes, pan/zoom/autozoom the window.
Handy tip: Select a viewer node (or the composite output node) then press L to select linked nodes. This will show you all the nodes in the noodle that contributed to the image output.
Whether you're new to the Blender Foundation's popular 3D modeling program or a seasoned graphic artist just interested in better acquainting yourself with the application, you're sure to be well served by this free video tutorial. For more information, including detailed instructions, take a look!