What is the difference between an antenna and a booster?
An antenna is a passive device that is attached to a piece of wireless networking gear. It helps to focus and concentrate the wireless signal in certain directions which can help in reaching further distances. However, it does not put any additional energy into the broadcast - it just takes whatever energy is being put into it and concentrates that in a specific direction. For omni-directional antennas, the energy that is normally sent straight down and straight up is focused into a horizontal plane, extending the reach of the wireless device horizontally. For uni-directional antennas, the energy is all focused in one direction which allows much greater distances to be achieved.
A booster on the other hand actually pumps more energy out, extending the wireless coverage all around. Boosters requires an antenna to broadcast through. One way to think about it is that while the type of antenna determines the shape of the wireless signal field, the output power determines the size of that field. An antenna booster increases the output power.