What is a meter?
The meter is the SI base unit of length and is equal to 100 centimeters or 1,000 millimeters. It was originally defined as one ten-millionth of the distance from the North Pole to the equator along the meridian through Paris. Since 1983 it has been the distance light travels in a vacuum in 1/299,792,458 of a second.
What is a micron?
A micron is one millionth of a meter, or 0.000001 meters. Its symbol is µm, the Greek letter mu followed by m.
'Micron' is the older name for the micrometer, and the SI dropped it in 1967. It survives on filter ratings anyway – a 5 micron filter catches particles down to about 5 micrometers.