) is a variable being assigned whatever is on the other side of the equal sign. As you can see, each line has several commands that are put together with periods.Looking at v1 and v2, you can see that each one is slightly different, as v2 adds a few additional filters. The important thing to note is that both v1 and v2 are separate video feeds at this point. v3 takes these two video feeds and combines them. This same method of combining two videos is done once again with v4a, v4b, and v5. In the end, the script returns the finished video, v6.
To use this in your own script, all you need to do is copy and paste, and of course change the plugin and avisource locations. If you already have an IVTC method in your script, then just replace the "SeparateFields.SelectEvery(10,0,1,2,3,4,5,6,9).Weave.AssumeFPS(23.976)" portion of both v1 and v2 with your own method, using the same syntax.
I hope that makes sense to you. If not, maybe laserschwert can explain a little better.