Bubblers are considered to be the smaller version of your typical bong. In terms of shape and size, bubblers are somewhat of a mix between a hand pipe and a bong. 

Like a bong, a bubbler is another type of water pipe with very identical functions such as filtering smoke and producing smoother hits but resembles a pipe in the sense that it uses a carb instead of a slide to draw out the smoke. 

Some people prefer bubblers simply because of their compact size as they can easily be carried and transported at your convenience.