It is nice to say hello back to others.
Paul is walking through a park when he's about to pass by another man, Ken who says hello to him.
Paul wants to greet Ken.
Paul looks Ken in the eye and tells him hello and says that it's a nice day.
Paul sort of looks down at the ground as he gives Ken a quick wave without saying anything.
Ken smiles and agrees with Paul that it's a nice day and wishes him a good walk.
Ken thinks Paul is a little weird to be so shy and is miffed he wasn't enthusiastic in his greeting.