Ok so this expac comes with a new town, western-themed clothes and furniture. The town has that old West / Arizona kinda feel to it. There are wild animals here and there (rats, racoons, pidgeons, chinchilla, lizards, snakes, turtles, hawks, falcons, etc) that you can watch, interact with. Some you can befriend and take home. There are options to adopt dogs/ cats/horses from shelters or from neighbors. Like in any Sims game, you have to build relations with the animals, these relations lead to more ticks, opens new options for the animals, etc. There are new pet-themed traits and LTWs. All in all, a little bit for any/all animal lovers - but this expac is really focusing on the horse (Im guessign since this is it's first intro into the Sims).
Horses can be built for speed and agility then put into races/competitions for money. They have their own lists of LTR that are exclusive to them while dogs/cats share the same type of (less exciting) LTRs. Even the smallest of the pets require care and like real pets, just bringing them home isnt the end of the road. Terrariums must be cleaned, wood chips and food pellets must be replaced. You can teach your birds to talk (which I thought was a hoot) and they'll say all sorts of things as people pass by them.
While some of the expacs are gimmicks (World Adventures, Ambitions) and some are more genre-related (Late Night), imo, this one adds to the overall Sims experience. If you live in a rural area especially, you can appreciate waking up to find deer eating at your garden, racoons rummaging your garbage can or the occasional stray dog tearing your morning paper apart. Or walking out your door to find people walking their pets to the dog park.
There are unicorns as well that act pretty much like horses except they have super long life spans, magical abilities and have an irridescent glow when they move. There are certain conditions needed before you can own one, and you have to find them. They are located throughout the map and only during certain times. Once you meet the conditions you can seek one out, or like in my case, you can get really lucky and they'll show up on your front lawn one night and eat all your apples and carrots while waiting for an invite inside.