Sram:

when SRAM launched our road technology from scratch they reapplied their MTB proven SRAM 1:1 actuation ratio (shifter cable travel : derailleur movement) for 10 speed rear shifting. Easy actuation helps to simplify/stabilize the uneasy act of balancing rear derailleur hanger design, tight cog spacing and exact cable tension. The result: the easiest index shifting system to set up and it stays that way.

Zeroloss simply means, well, zero loss when you push on the lever, for an upshift or down shift, the cable is engaged instantly zero loss of movement. There is no middle-ground where youre waiting for the shift to come. Gear changes are instant and precise.