Household Cavalry are a type of melee cavalry in Empire: Total War.
The royal guard cavalrymen are all gentlemen, hand picked to protect the person of the sovereign.
Royal guards are elite, but they are also a court regiment where appearance is as important as fighting ability. As gentlemen they are hardly expected to associate with the common sort of soldier, and this does not make them popular or respected with the rest of the army. They are also often unloved by the general populace too, as they are the last line of defence for the royal family, and this may mean that they are sometimes required to turn their swords on their countrymen to put down domestic trouble.
Historically, perhaps the oddest sounding of the various royal guard cavalry regiments were the curiously named horse grenadier guards. Common sense would seem to indicate that these men would only ever get to throw their grenades once, before their horses took off at speed towards all points of the compass! In British service the Household Cavalry regiments did not, and do not, have sergeants: they have a rank “corporal of horse”. The word “sergeant” has the same origins as “servant”, and no gentleman, even a private trooper, is ever a servant.
Household Cavalry are the generic elite heavy cavalry available to all minor Western factions and some major factions. Much like General's Bodyguards, they inspire nearby troops. However, they are more numerous in number and more capable in a melee.