So, I'm fairly new to Mathematica; sorry if this ends up being a very dumb question. I've been trying to simulate and plot electric field lines from point charges in Mathematica. The first resource I found is Wolfram's Electric Field Lines Due To A Collection of Point Charges, but I've been having trouble figuring out how one would incorporate more source charges. What I think I'm not quite understanding is the first lines of code defining the electric field - I don't understand how p and pp are being defined, or why it wouldn't work to simply add a third term along the lines of qi and so on. If anyone can offer any insight, I'd be very grateful.

 eeX = Compile[{{q, _Real, 1}, {pp, _Real, 2}, {p, _Real, 1}}, 
        Sum[{-((q[[i]] (p[[1]] - pp[[i, 1]]))/
((p[[1]] - pp[[i, 1]])^2 + (p[[2]] - pp[[i, 2]])^2)^(3/2)), 
-((q[[i]] (p[[2]] - pp[[i, 2]]))/
((p[[1]] - pp[[i, 1]])^2 + (p[[2]] - pp[[i, 2]])^2)^(3/2)),
 {i, Length[pp]}]]