Muggles' Guide to Harry Potter/Magic/Scourgify

Overview
Scourgify is one of the cleaning charms, used to clean foreign material off surfaces.

Extended Description
In Harry Potter and the Order of the Phoenix, we see it a couple of times; Tonks uses it with limited results to clean Hedwig's cage (she admits that she's not very good at that); and Ginny uses it to clean up the Stinksap that Neville's Mimbulus Mimbletonia has sprayed around the compartment of the Hogwarts Express. It is also used to "wash out" a young Snape's mouth in Harry Potter and the Order of the Phoenix.

Analysis
Scourgify seems to be limited to surfaces; it cannot restore spilled liquids to a container, only eliminating them. It also is not used to remove foreign matter from a container; Evanesco is used for that – which may be why Tonks' attempt to clean Hedwig's cage, a container, does not succeed. There is also a charm Tergeo that seems to be used for almost the same purpose.