What is meant by downlink?

Uplink frequency is the frequency at which, the first earth station is communicating with satellite . The satellite transponder converts this signal into another frequency and sends it down to the second earth station. This frequency is called as Downlink frequency.

It say basically the power at ground stations is more as compared to power available at satellites .So generally frequency for uplink is kept higher than the downlink. There is greater attenuation due to rain when the signal frequency is high.so downlink is also kept at lower frequency.

: to transmit (data) from a spacecraft or satellite to a receiver on earth .