Hey can u help me understand ?

hey right im 16 and iv never been in a proper like bf and gf relationship. but alot of my guy friends say that im the girl they would shag and snog but woulndnt make me there gf? y is that? yeh i have snogged a few of my guy friends 2 see if it would go futher in 2 gf and bf but never happened? y is that? is it true guys that u sometimes have girls u would go 2 and have a snog/shag with but wouldnt go in a relationship?