As a trainer this is my starting point with every new client or group. It can be done with a dumbbell or kettlebell. A goblet squat shows me, as a trainer, my clients’ strengths and weaknesses and from there we build.
Holding the dumbbell or kettlebell in a goblet position engages the shoulders before you squat. Hugging the weight close to the chest forces you to pull those shoulders back, activating your rotator cuff, spinal, pec, and scapular muscles. As you squat, the weight will want to pull your chest forward. To counter balance this, the erector spinae group, trapezius, latissimus dorsi all have to contract to ensure your back doesn’t crumble into a forward flexed and rounded position. Which means you are strengthening your shoulders and core. This is an important aspect of any squat if you want to go on and lift heavy front or back squats.