The "style" determines how forceful the audio material should be hit by the limiter:
The soft limiting style ensures a smooth and transparent limiting process. We suggest using it for content that should sound natural. Generally, this style delivers clean limiting results for a wide range of material.
The neutral limiting style aims for a good balance between a punchy and a transparent sound. It works well for most audio material and makes your mix sound compact without changing its overall character.
The hard limiting style helps to add some extra punch to your track. While keeping an eye on the limit, the hard style allows to really squash your material and lets your tracks sound aggressive and dense.