In 1PDG tags work a bit differently comparing to my other generators (e.g. Perilous Shores). The idea here is that you need to specify only aspects of the dungeon you care about. For example, if you need a totally random dungeon, select no tags. You won't get a featureless dungeon, instead your empty choice will be augmented with a few random tags. If you need a large dungeon, but you don't care water, select the "large" tag and sometimes the "dry" or the "wet" tags will be added. But if there has to be no water, select "dry". And so on.