Why do PP slides move on my MacBook yet remain static on data projection, when yet not w Windows?

[iMore Question]

If one then touches the mouse pad the picture moves on, but if making a presentation with one's back to the large screen one will assume that the data projector is showing the same as on the MacBook Air screen - can't keep looking round. The Windows PP projection moves on immediately.

 

[Just_Me_D]

I don't know, but hopefully, someone who does will respond soon.