Intrusion prevention system
Also known as IPS, IDS
A control that watches network traffic for attack patterns and blocks or alerts when it sees them.
Detection systems alert; prevention systems block inline. Both match traffic against signatures of known exploitation attempts and against behavior that deviates from normal protocol use.
Tuning decides whether it helps. Left at defaults it either generates noise nobody reads or blocks something legitimate at the worst possible moment.
Where this comes up
Intrusion prevention system sits inside our networks and infrastructure work. If you are trying to work out what this means for your own environment rather than in the abstract, that is the page worth reading next, and a short call will get you a straight answer faster than either.