The values for those fields would usually be a boolean indicating whether you voted or not. For a primary it might have the party, meaning which party's primary you voted in.

For a Get Out the Vote operation it's very valuable to know how consistently people have voted in the past. If you look like a supporter but you vote inconsistently, I might call and ask if you need a ride to the polls. If you already vote every time, I'll allocate resources elsewhere, or ask you to donate/volunteer.