What is uplink? downlink?

Uplink is the signal path from an earth station to a satellite.

The opposite of uplink is downlink. Downlink is the signal path from the satellite toward the earth.

Uplink Frequencies

Satellite Band        Uplink Frequency

C Band                 5.925 - 6.425 Ghz
Ku Band                14 - 14.5 Ghz
Ka Band                27.5 - 31 Ghz