Plugs and gauges are often confused with being the same, probably because of the causal use of the two words, most especially when it comes to ear stretching and piercing. At times, you will see children in grocery stores asking for gauges while what they should be looking for are plugs.
This is because the size of a gauge is bigger than that of a plug. A gauge, in this context, is never a material you can fix to your ear, but an instrument used to determine the volume of the jewelry like plugs, mostly in terms of thickness.
To understand this better, think of plugs as the jewelry that exists in different gauges, colors, shapes, and designs. What you can easily make of this is that plugs with smaller gauge are less expensive compared to plugs with a larger gauge. The gauge of the plugs also depends on the materials used in making them.