Puer aeternus is Latin for “eternal boy,” and it refers to a personality for the type of man who never grows up emotionally. Some say there is a related archetype for women: puella aeternus. It is called the flying boy because the person is always trying to “fly away” (escape) from adult-life entanglements: jobs, relationships, debts, etc. Also, many examples of this archetype are associated with wings or flying: The Roman god Mercury (Greek Hermes), with his winged helmet and winged ankles; 
Peter Pan, who escapes into a fantasyland; 
Icarus, who was warned not to fly too close to the sun with his feather wings held together with wax, but did and fell; 
the Little Prince, who lives on a distant planet and meets an aviator; 
etc. In its positive aspects, the puer is able to create lots of new things and helps in transformations of other people and things into new manifestations. Hermes invented the lyre (forerunner of guitars) out of a turtle. 
The archetype is also the messenger of the gods or bridge to God (psychopomp). Hermes/Mercury also has a symbol associated with the healing arts and with commerce: the caduceus, a staff entwined by two snakes. 
He happened upon two snakes fighting or copulating (depending on the version) and separated them with a staff, then rejoined them with the staff. So he was associated with healing and bringing peace and also with ambiguous sexual identity.
So if you meet someone who is always looking for something new, just know they can help you to move onto another stage of your life…but they probably won’t be there with you for that new stage.