Forward collision warning (FCW)
Alerts you when you are closing too fast on the vehicle ahead.
Forward collision warning uses a camera or radar to watch the vehicle ahead and alerts you with sound and lights when you are closing too fast. It buys reaction time; the braking is still up to you.
Many vehicles pair it with automatic emergency braking, which applies the brakes itself if you do not react. On spec sheets the two are distinct features, so check whether a trim has the warning alone or both.