The term is confusing, we know. A "cavity nester" simply means a bird that nests inside an enclosure. In the natural world, it could be something like an old woodpecker hole in a dead tree. In today's world, it could mean a birdhouse.
Only certain species use birdhouses. In North Texas that's wrens, chickadees, titmice, bluebirds, woodpeckers and swallows (including purple martins). Try as much as you like, but a robin or cardinal won't ever nest in a birdhouse.
It may not seem like it, since a birdhouse is modeled after something like a hole in a tree, but dimensions are critical. Enough floor space for their nest. Enough depth to keep eggs out of the reach of predators. A properly-sized entry hole. If things aren't 100% right, cavity-nesting birds just look elsewhere. Most of them don't have the strong bill or the excavation skills to 'remodel' a nesting place that isn't totally right to begin with.
Ideally a large, dead tree will become home to a cavity-nesting bird family . . . maybe several. (Homeowners experienced with encouraging bird-nesting will sometimes remove most of a dead tree, but leave a 10 ft. tall 'stump' for the birds). Where no trees or tall stumps exist, however, cavity-nesting birds look for birdhouses.
Whether building or buying one, the dimensions and construction are vital. If wrong, the house may remain empty. Many species of birds in North Texas are more robust than similar species elsewhere, so make sure the entry hole is properly-sized for this area. Not too big though, or you may get unexpected residents. Also, you'll want a simple way to see what's happening inside. Forget a perch, too. That just makes it easier for unwanted visitors—songbirds can easily cling to the house itself.