I will try to help you.
First of all, somewhere in your openings book should be an explanation.
If not, they mostly follow a similar format. I am assuming that you understand chess notation. Take an opening, say the Ruy Lopez. One the first page will usually be a diagram of the defining position for this opening along with the moves...1)e4, e5 2)Nf3 Nc6 3)Bb5. One of blacks most common responses is 3...a6, so first column in the openings table might show a6 followed by a number of moves. Since this is a common response, the next dozen columns may have a dash for this move, which simply means that the move is 3...a6, then followed with a bunch of different moves. Two very similar lines may use much of the same moves until they diverge: the second one of these will have a large number of dashes in the column. I think that they do this for 2 reasons. First, it is probably simpler and quicker to print. Second, you can tell at a glance if the opening line that you are studying is similar to other lines.
Hope this helps.
Can anyone help me with knowing how to read opening tables?
The wikipedia article 'Chess opening theory table' is helpful, but then when I consult 'Chess Openings the Easy Way - MCO-beginners' I'm lost. And unless I'm missing it, MCO-beginners doesn't explain how to read the tables.
Help!