RDB,
Coin popping involves the use of a screwdriver or similar tool (there are devices made for such a purpose) to extract a coin from the ground without digging a plug.
Shermanville, with all due respect, some coins simply cannot be popped out with a screwdriver. Nowadays, many detectors are capable to detecting coins that are deeper than a screwdriver is tall. Even if you could try to pop out a coin at eight inches, it'd be damn near impossible.
Yes, coin popping can and does damage coins. Typically, people pop out surface coins, which in most cases end up being clad coins anyway and are not worth more than face value. Any coin les than 2 or 3 inches deep should and can be popped out, as digging a shallow plug can prove destructive to a nice lawn (cuts up the roots).
I haven't used a screwdriver to pop coins in a while because I'm not so much of a clad hunter anymore. I usually skip over the shallow stuff and seek out the deeper, older coins. I do dig quarters, though, and I can usually pop them out with the tip of the Lesche digger.
Hope this info helps!
Joe