However, I don't understand what is a raster attribute table (RAT). The resources I found so far mostly explains how to build/delete a RAT and errors associated in the process, rather than what it is and what it's used for.
What I've figured out so far, is that RAT is only defined if the raster in question is categorical (in other words integer valued).
What is a raster attribute table? Can it have arbitrary number of columns and as complex as vector attribute tables?
How is RAT different from the attribute table of a vector dataset, and what is RAT typically used for?