It's hard to pin down exactly who this figure is supposed to be. The picture on the package shows General Veers (the guy who led the AT-AT assualt on Hoth), but he has the brownish-grey uniform of a higher rank. The black uniform is of a lesser rank, a commander, and could also be the dress uniform for a stormtrooper. Well, what are ya gonna do? It's the old line - little things like this didn't get in the way of some kid saying, "I don't want him, I want a stormtrooper!"
The Imperial Commander comes with a standard issue stormtrooper type-rifle, like many, many, many of the other old Star Wars figures. It also came on an ESB and ROTJ card.
Why should you own this figure? Five reasons:
1. Another man in black. You can't go wrong in black, Jack.
2. The Empire needs bureacracy.
3. Your Vader figure can't be around to command every Imperial.
4. You can have this figure reenact a number of Imperial officer/Vader choking scenes. Great fun!
5. That cap is damn stylish.
I kind of already said part of it - the picture is General Veers, who is a higher rank than Commander. Captain is the next step up from Commander in the Imperial Navy. However, Imperial Commanders have made appearances in all of the original movies.