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. It does not however 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 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.

Boosters on the other hand actually pump more energy out, extending the wireless coverage all around. A booster requires an antenna to broadcast through. An easy 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. Most Base Stations and wireless routers, including Apple's AirPort Base Stations, have an output power of 32 mW. MacWireless's Antenna Boosters increase the output power of base stations and wireless routers to up 500 mW. That is an increase of more than 15 times.