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".