FPV (First Person View) allows broadcast view from drone camera through a video transmitter in real time. For FPV system you need special components, such a camera, goggles, but also transmitter and receiver.
A video transmitter (VTX) is connected to drone camera and transmits the video signal from drone to you during flight. Using the transmitters it's neccesary to consider the frequency your FPV transmitter runs. 5.8Ghz is the most popular as its legal to use in most part of world and it enough for fly up within visual range of your craft. However, in depends of frequency, suitable antenna is required.