A micron, or micrometer/micrometre or µm, is a measurement used in sciences, industry, and English speaking countries.
Have you ever had to measure something that is so small it doesn't make sense to measure in centimeters or millimeters? That is where microns come in.
1 micron is the same as .00003937 inches, or 0.001 mm.
Between 1 μm and 10 μm:
Over 10 μm: