What does 'Hypo-dermic needle effect' & 'Synergy' mean?

The Hypo-Dermic Needle Theory also known as the Magic Bullet Theory constructs the idea that the mass media has a direct power over its audience.  It suggests that media messages are injected straight into the audience meaning that they're immediately influenced by this message hence the name Hypodermic 'Needle' theory.  It can also be described as the media message being a bullet, fired from the media gun into the viewer.

Synergy is the result of two or more people or groups working together to make a combined effect that is greater than the one person can achieve.  It's basically uniting people together and achieving more than usual.