CBM - Counter-body Movement (or Contra)
CBMP - Counter-Body movement position.

Since you are a beginner, I will not go into details. Simply put, CBM deals with body movement - a case where the left foot and the right shoulder are swinging in opposite directions. An example would be the reverse-turn in a foxtrot, or the basic walk step in the Tango.

CBMP however deals with foot placement. To understand this, you must understand that standard dances are supposed to have two tracks, one for each foot of the dancer. Your knees are meant to be together, and the feet point straight along the tracks. If however, a figure requires CBMP, it means that one foot will leave its track and be placed either on or across the track of the other foot. The feet will still point in the same direction, mind you, but they have now 'crossed' tracks.

This concept is also applicable to latin dances - say for eg. the Cha-cha, where you use CBMP for the 2&3 step of the basic. There is no CBM in latin dancing, only CBMP.
However, standard dances use both CBM and CBMP.

And to add one more confusing nugget, CBM does not necessarily mean CBMP is involved, but when you perform CBMP, CBM is also incorporated.

You will surely understand this more as you progress along with your dancing. Good luck.

Sri.