In storage networking, Fibre Channel zoning is the partitioning of a Fibre Channel fabric into smaller subsets to restrict interference, add security, and to simplify management.
Soft zoning restricts only the fabric name service, to show only an allowed subset of devices.
This requires efficient hardware implementation (frame filtering) in the fabric switches, but is much more secure.
That stated, modern switches will employ hard zoning when you implement soft.
A zoneset is merely a logical container for the individual zones, that are designed to work at the same time.