This is a Weakaura to help coordinate using Netherweave Nets on the Coilfang Striders in the Lady Vashj encounter.
There are two custom options you need to select from: Net Position and User Count.
Net position is the position in the overall order that you will use your Netherweave Net.
User count is the total number of people that will be using Netherweave Nets during the encounter.
Other than that, it is very much a plug and play addon. When it is your turn to use a net, the Nethweave Net icon will appear on your screen for 3 seconds.