And #"anions"# are so-called because they migrate (across a potential difference) to the positive terminal, #"the anode"#. And, likewise, cations, positively charged species, migrate to the negative terminal, #"the cathode"#.
Now we use positive and negative signs for electric charge by convention. The point is that electrons and #"nucular"# protons have opposite electric charge. I have written here before that it would have made much more sense to assign a POSITIVE charge to electrons. Why? Because there are far more chemists than particle physicists, and it would have saved generations of quantum chemists from getting the wrong sign on their answer in a many electron problem simply because they counted odd instead of even or vice versa in a quantum chemistry problem.
We are stuck with the convention now.
