See the
Geo code article on the wiki. It explains what they are ("The purpose of geo codes is to enable leadership to group members and households by geographical location for reporting purposes") and some possible conventions for using them.
Basically, if you are a stake clerk and you ever think you might do a ward or stake boundary change, they can be very useful.
If you are a ward clerk, they have some possible uses (a couple of suggestions are at the bottom of that wiki article). But if you don't have those particular needs, there's no reason you
should be using them; only use them if they improve your work. I would note that some stake clerks may request that ward clerks divide the ward into areas using Geo codes, but unless you have been asked to do this by your stake clerk, that would not apply.
Questions that can benefit the larger community should be asked in a public forum, not a private message.