Ellipses assignment?

[cosmic_kid]

I've been getting into WoW addon development and for the moment, I'm mainly looking through other people's code to understand what's going on. I keep seeing this type of thing all over the place and I can't, for the life of me, figure out what it means.

local _, ns = ...

They then go on to use the ns variable, but I don't know how it has any data in it. What are they assigning it to exactly?