Why is oxygen bubble formed on positive terminal and hydrogen bubbles on negative terminal of the battery?and what do you mean bye "dissociates"

1.Hydrogen gas bubbles form on the negative end of electrode, and the negatively charged OH^- ions migrate away from the negatively charged electrode.

2.The oxygen molecules form bubbles at the electrode, and the protons migrate away from the positively charged electrode.

Hence the protons produced from positive end combine with the OH^- ions from the negative electrode, and form water molecules again. Thus this arrangement of electrode allow the cell reaction to work continuously.