Printing process - 6 colours

hi,

I’ve got a design brief which specifies that “6 colours may be used” and also mentions that the company logo prints in 3 colours - Process Cyan, process black and PMS 2757.

firstly, i don’t really know what the PMS thing is… is that pantone colour? Also, when it says 6 colours can be used, does it literally mean that? or does that include diffent shades/tints of the same basic hue?

thanks
Stuart