What's GetTypeFlags() and SetTypeFlags()?

There's a JED plugin that does the following, what are the commands that does the same for each of the functions?

• Gets the number of sectors in a level.
• Gets the number of surfaces in a level.
• Gets the number of things in a level.
• Gets the number of certain templates used in a level.
• Sets a color map to a sector.
• Sets a mat to a surface.

Why is cog called "cog"?