Pin gauges and slicing gauges fall under the umbrella of marking gauges and are primarily used to scribe lines for joinery. Pin gauges are simple and inexpensive. They consist of a steel pin mounted near the end of a bar that’s most often made of wood. Without refinement, the pin makes a V-shaped cut that tends to rip the fibers when marking across the grain, as for the tenon. On slicing gauge (often called cutting gauges), the pin is replaced by a knife-like cutter that typically is flat on the outside face and beveled on the inside. This wedge shape pulls the main body of the gauge tight to the edge of the stock and discourages the blade from wandering. This profile also leads to tighter joinery because bevel is on the waste side of the cut.
A modern variation of the slicing gauge is the wheel gauge, which uses a beveled circular cutter mounted at the end of a bar or a round steel shaft. The cutter does not rotate during use. When a section of its edge dulls, it can be loosened and rotated to expose a new section.
The all-metal versions of the wheel gauge come with disk-shaped fences that typically are smaller than the rectangular wood fences common to traditional slicing gauges. To me they feel awkward and provide too little bearing surface along the edge of the workpiece. Still many folks I know would be reluctant o give theirs up.
If you have a pin gauge, you can convert it to slicing gauge. Just file the pin’s outside face flat and its inside face on an angle to form an edge that actually will cut the wood.