What is the meaning of Under The Greenwood Tree by William shakespeare?

Under the Greenwood Tree is a song sung by Amiens in As You Like It, as follows:

Under the Greenwood Tree

Who loves to lie with me

And turn his merry note

Unto the sweet bird's throat

Come hither, come hither, come hither

Here shall we see

No enemy

But winter and rough weather

Who doth ambition shun

And loves to live i' the sun

Seeking the food he eats

And pleased with what he gets

Come hither, come hither, come hither

Here shall we see

No enemy

But winter and rough weather

The song encourages the kind of lifestyle lived by the exiles in the forest of Arden. They shun ambition by not living a court life, live outdoors "i' the sun", singing, lying under the trees and eating what they can find in the forest (and being "pleased with what [they] get"). In the forest there is no Duke Frederick who would kill them--all they have to worry about is the cold and wet--"winter and rough weather"

They were sort of the original hippies (without the drugs) and are sometimes played that way.