Well, the gist of it is that whatever is on the right side of the equation must also be on the left side of the equation. The left and right sides have to have the same number of the same atoms. The compounds will of course be different, but the atoms themselves will stay constant. When talking about ionic equations, in addition to the number and type of atoms being the same, the net charge must be the same as well. So if the left side of the equation has an overall charge of +2, the right side must have an overall charge of +2 as well. Does that make sense?