Would generally be used as a disconnect switch ahead of equipment. The 3R rating means that it is rainproof, and suitable for outdoor locations when properly installed.
These switches may be fused or unfused, 2 or 3 poles, and may be used as a service disconnect if marked as suitable.
Incoming power is fed to the top lugs, and the load conductors are landed to the bottom lugs. There may or may not be a lug for a neutral conductor present.