Full Metal Jacket rounds, otherwise known as “target ammo”, “range ammo”, “FMJ”, etc, are a lead core bullet encased and surrounded by a copper layer, hence “Full Metal Jacket”. They are cheaper to make than hollow points, and for pistols, generally come in a box of 50.
Hollow Point rounds, or “defense ammo”, have a hole cut out of the tip exposing the lead core, hence “hollow point”.
The purpose of hollow point ammunition is not, contrary to popular belief, to make the bullet expand to do more tissue damage. While that is indeed a beneficial side-effect, the real purpose is to slow the projectile down to prevent over penetration.
Over penetration: When the round you fire at the bad guy goes through his body and potentially hits an innocent bystander.
“Can my target rounds stop a bad guy?” — yes, of course. But you run an increased risk of hurting people you didn’t mean to, and generally, this is considered reckless and could be considered a crime in some situations depending on the outcome of your self-defense trial.
Defense ammo is for defense, target ammo is for targets.