All are "austenitic" grades of stainless.
The 18-8 types are considered standard grades suitable for fasteners not exposed to salt water conditions.
All contain varying amounts of nickel & chromium for corrosion protection in most non-saltwater conditions.
Type 305 has higher nickel content to reduce magnetic properties and protect against head snapping of screws during cold weather installation. Type 316 contains molybdenum for salt water corrosion protection.