Fins that you can wear on your feet come in two types:

Standard is the type which fits your feet as it is.  Mostly recomended for recreational use and snorkling.

Proper type is the one that fits on top of a diving shoe.  This is the one I recomend for anybody who is taking diving seriously.

The diving boot gives you a chance to wear fins easier.  gives protection on beaches while you are getting in and out of water.  and Most importantly allowes you to keep your feet warm when you dive in colder waters.