Here's where things get fun. Just like the number of reps, 3-6 sets is the best range of volume for this training method. If you like your workouts paced like clockwork, take 30-60 seconds rest between each exercise.
The natural attraction between positive and negative keeps the ions surrounded by water molecules and therefore dissolved in solution. Many biochemicals are either polar molecules or charged ions (or both) so water makes an excellent solvent for them.
A solvent is a substance which dissolves a solute. When a solvent dissolves into a solute, it creates a solution. If i pour salt into a cup of water. The salt is the solute because it's being dissolved and the water is the solvent because it is doing the dissolving. The saltwater is the solution because that's what the solvent and solute make. A way to remember is that if you spilled salt on the table you need to get rid of it.