Basically all a DB (Drop Bracket) Lift is is a glorified subframe spacer. They install a Drop Bracket, which puts the Lower control arms lower than the original location, they then use taller spindles to achieve a lifting effect of the vehicle while retaining most of the components (usually extended shocks or adapters are installed as well) that are used in steering and such.
You tend to have little to no gain in ground clearance as the clearance is attained through the larger tires you can install. The kits themselves act more like body lifts than a suspension lift and are very dependent on tires to gain clearance. That being said, the suspension geometry is affected somewhat (usually more negatively than positively as I will explain in a bit) and the angles of the CVs become an issue. This can be corrected with things like Diff Drops (if I remember right), these are the most common lifts you see on Tacomas, F150's, GM Trucks, ect ect because they can jack a truck up 12+ inches and let you slap on 35's, 37's, ect on the truck and not have to worry too much about compression/flex rubbing.
A lot of people (including myself) tend to look down on them as "cheapo" (though to be honest some are more expensive than a suspension lift kit) lift option and don't consider them as capable off-road as some other options. The main reason for this because the suspension geometry change doesn't allow as much true compression and flex as say a suspension lift like OLW 2.5" does. This is because all the kit is designed to really do is increase the space between the upper and lower control arms to achieve a lifting affect, the lower and upper control arms are still the same length and the suspension for the most part will still bend and flex close to stock (I say close, because there's a bit more to the story than that...)
Take a look at a true Long Travel Suspension System, see that they give you new control arms among other parts, this is because to gain more travel and potentially more flex, you need to adjust the suspension geometry of the vehicle. Look at Baja Trucks, They have that insane lift mostly from the insanely non-factory suspension geometry they have that allows huge amounts of compression and flex. Even Rock Crawlers with SFA (Solid Front Axles) have a serious amount of suspension geometry modification to allow the insane amount of flex they use.
