Could you explain "borderline personality disorder" in layman's terms ?

Borderline PD: These people tend to be intense, dramatic, emotional and erratic. They show marked impulsivity and instability of - mood, interpersonal relationships, and self image. Often seen in young adults, this can be very dangerous as fluctuations of feelings toward others and self are extreme and intense. Life can be difficult for the person and everyone around them. Love/hate - on/off.

Borderline: Intense fear of abandonment, being manipulative, impulsivity, a tendency to think of people and things in all good or all bad terms, self mutilating behaviors, drug and alcohol abuse, sexual impulsivity, a profoundly disturb sense of self, and extreme emotional volatility.