Hi BB , when staring at you your dog is probably trying to understand you while studying your 'body language' for clues.
My Puffin stares usually when she is slightly confused and isn't sure of something, when she wants me to understand something like 'will you play with me', or 'I want to go for a run /have my lunch now ', also when 'challenging' me in situations like stealing a tissue which I remove by distraction with another toy.
Puppies soon learn to equate body language like stance/ facial expression/ voice tone with how a human (and other dogs) will react. Smiley face good cross face bad .