It's easier to use an actual coordinate and explain it. The charts always have the zone they're in. The first four digits represent the number of the horizontal line of the grid, this would be line 4372. This is useful to project or to read the distance from the lines on a chart. Just divide the grids in one thousand imaginary units, it's not necessary to work with meters, or know how long a meter is.
Meters are there for projection purposes only.
Just to know where you are, and comparing coordinates with those of a chart. To record where you have been, so you can later mark it on a chart or save it on file for future use. Remember that a GPS receiver takes longer to acquire the location the first time you turn it on during the day, so turn it on for a few minutes before you leave for the trail. Having a chart of the area you are going to ride, you can outline the intended track, or individual spots you want to visit. You should, however, take the charts with you.