Light snow stranding (snow up to mid-wheel) is often self-recoverable. Rock the vehicle: alternate forward and reverse with light throttle, no spinning. Place floor mats, cardboard, or sand in front of the drive wheels for traction.
Medium stranding (snow up to mid-door) is borderline. You can sometimes still rock out with persistence and shoveling. The risk is digging deeper if wheels spin without traction.
Heavy stranding (snow up to the windows or beyond) is a tow situation. Don't waste time trying to rock — call recovery and stay warm in the vehicle.
Things to avoid: spinning the wheels (digs holes), wedging traction aids that get destroyed by the tire spin, attempting to push from outside (impact injury risk if the vehicle suddenly moves).
Things that help: a small foldable shovel in the trunk, traction mats (yellow plastic mats designed for stuck-vehicle recovery), winter tires (often the difference between stuck and not stuck).