The advantages of green screen are limitless. Green screen allows filmmakers to do almost anything so long as they put in the work to ensure they get it right. The biggest advantages of using a green screen are:
It allows for exciting and otherwise-impossible scenes to be produced, expanding film making possibilities and language.
It can protect actors by keeping them in the studio and away from the dangerous environments depicted using green screen technology.
It can allow actors to appear on screen together even if they film the scene separately. This helps when scheduling is a concern.