Good enough to hang out with but not good enough to fuck (usually due to lack of good looks). A step up is friends with benefits which is good enough to fuck but not good enough to date (usually due to lack of social/economic status).
Ahmed: "You get anywhre with that girl? You must! She was alone at your place all night!"
Ping: "Nah, she'd rather be just friends. Said so herself! I did see that she was wearing a green g-string when she reached over for another glass of the Champagne!"