DAW = Digital Audio Workstation.
In the routing section of Saffire and Scarlett Mix control the term "DAW" in the drop-down menus refers to the outputs of the recording software that you are using.
By default, most audio software will output to channels 1 and 2. These are represented in Mix Control as "DAW 1" and "DAW 2". So for example, if you choose outputs 5 and 6 in your DAW software this will come into Mix Control as "DAW 5" and "DAW 6".