What does the popular American phrase, "Yolo" mean?

[Delicia]

I have been recently checking the "Twitter", the "Facebook", the "Vine", the "Myspace" the "Tumblr" and last but not least, the Google owned corporation, the "YouTube." I have been hearing multiple things about "Swag." What does this mean? The only clue I have is every time I hear the phrase "Swag" it has to do with a white, or more popularly, african male. They also tend to have on a "Bull's SnapBack" large, "gangster" "Osiris" shoes, tight "skinny jeans" and a pop culture t-shirt, or jacket. This word, "Swag" really interests me and I would love to learn about it more, so I can be "Dope Sh.it Fly" (As the kids would say.) Thank you.
I do only love Oregeno! Thank you for teaching me what the mysterious "YOLO" meant. I will now fulfill my dreams of owning my own restraunt, where Oregeno will be a popular ingredient in all my dishes.

[bobcats]

you only live once

[bobcats]

Your Only Love: Oregano

It's a popular phrase among cooks.

[Niki]

You Only Live Once

[Lulu]

You Obviously Love Oreos.

[Lulu]

you only lick once its a phrase to live by really.If you have a lollipop or ice cream cone remember only lick once.

[bee]

you only live once.

[Keith]

Are u that stupid? U have no social life. It means u only live once

[Nick]

you only live once

[William]

YOLO=You Only Live Once

Swag=coolness, style