Why VARA is a software modem developed by EA5HVK that uses OFDM (many parallel subcarriers) to move data over HF, VHF and UHF. It is most commonly paired with Winlink, the radio email system, as a transport protocol alongside older modes like ARDOP and Pactor. VARA HF fits in about 2.3 kHz of SSB bandwidth and adapts its speed to channel conditions, which is why Winlink gateways widely support it.
Watch out The low signal-to-noise weak-signal mode used for EME is JT65 or Q65 from the WSJT-X family, not VARA; VARA is aimed at throughput, not digging signals out of the noise.
VARA and Winlink go together: think 'VARA carries the mail.'