Rather than just give an enemy - or occasionally your character - a generic Life Meter, or show the exact number of hit points, some games will show the enemy taking damage on screen. Sometimes this makes sense and looks good, other times, not so much. The bad guy's armor having bullet holes in it is all well and good, but weren't you using a sword? Sometimes, this can even affect gameplay. Damage the enemy's laser cannon enough, and you'll disable his most powerful attack. Or perhaps discover that he's not left handed, or make him angry, and proceed to get your ass handed back to you.