namely, that the specific activites which a gal does with one person may not be available to all.

A good example is anal sex.  Some gals play down or totally ignore this practice on thier websites, but perhpas will engage in it with someone who will then describe a session with it but say YMMV.

When ever you do see this, you can not count on being able to engage in that specific practice.

so is the "self help center" and finally you could try the urban dicitionary. Lot of resources out there for you to explore.