To be more accurate, we will use the term High Fidelity System to refer to a pile of equipment including at least one source, at least one amplifier, and at least one speaker.
Common sources are turntables, CD players, tape players, tuners, and receivers.
A receiver is a tuner, power amplifier, and preamp combined. A common receiver has inputs for a turntable, a CD player, a tape deck, and perhaps one or two other sources. A receiver may have outputs for two speakers, or for more. A tuner is a radio receiver which can not directly connect to speakers. Sometimes, the radio in a tuner is higher quality than the radio in a receiver.