Straight Edge refers to a lifestyle choose to refrain from drinking alcohol, using tobacco products, using recreational drugs and also refrain from promiscuous sex. The term came from the hardcore punk band called Minor Threat. The singer lived that life style and wrote a song called "Straight Edge".

Minor Threat- Straight Edge

I'm a person just like you
But I've got better things to do
Than sit around and f*** my head
Hang out with the living dead
Snort white s*** up my nose
Pass out at the shows
I don't even think about speed
That's something I just don't need

I've got the straight edge

I'm a person just like you
But I've got better things to do
Than sit around and smoke dope
'Cause I know I can cope
Laugh at the thought of eating ludes
Laugh at the thought of sniffing glue
Always gonna keep in touch
Never want to use a crutch

I've got the straight edge

In the early 80's the punk scene divided. There were the classic punks, who were into heavy drinking and drug use and then were the clean, "straight" kids that made up the straight edge movement. The straight edge movement and hardcore music scene have always been linked. That how I first heard about it, check out this earlier  blog I did below.