Satellites use microwaves to transmit signals. Such signals should not be obstructed by any solid objects between the sender and receiver. The phase line of sight is often used to refer to this requirement for microwave antennas.
When using satellites line of sight is not a major concern - except at the point where the signal from the satellite has to enter the building. Satellite reception dishes are therefore placed outside and the signal is carried into the building by (typically coaxial) cable. The dish has a parabolic shape and focuses any signals that it reflects to the end of the arm attached to the bottom of the dish.
So, here we have a typical LNBF - mostly used to receive satellite television. The matchstick has been included in the picture to give a sense of scale.