In Happy Home Designer, you work for Tom Nook as a real estate agent. Unlike other Animal Crossing games you cannot wander around a town. You just have a little city filled with shops and other buildings to decorate. Animals also wander around the city, each with a different house theme. You pick a spot for their house to go on the map Lottie shows you, and then you decorate it how they want. That's really all you can do in this game.
If you aren't big on designing houses, I wouldn't get this game. But if you really like building and designing houses and other buildings, go ahead. I really like the game, but it can get a little old after playing for so long every day. And there aren't any goals to look forward to like in a regular game of Animal Crossing, as you can't fish or catch bugs and you don't have your own home.