"The term "non-manual marker" refers to a type of non-manual signal (that you do without using your hands) that influences (marks) the meaning of something else that you are signing. A non-manual marker is always a non-manual signal. But a non-manual signal is not always a non-manual marker." It is like non-manual marker is an umbrella term that covers all aspects of Thus, the reason we call one of the parameters non-manual markers (NMM) (Source).
YES/NO Question Expression:
When signing a question that can be answered "yes or no" you raise your eyebrows and tilt your head forward a bit.
"WH-Q" Question Expression:
When signing a question involving "who, what, when, where, how, how much, how many, which, or why" you use what is called a "wh" question facial expression. The "wh" facial expression "furrows" the eyebrows a bit and may tilt the head back a bit--while the body might lean forward a bit.
see Slides on Parameters of Facial Grammar below for more information