Molality is a measure of the concentration of a solute in a solution, expressed as the number of moles of solute per kilogram of solvent.
This is another way to express concentration, defined as the number of moles of solute per liter of solution.
This is the substance that gets dissolved in a solution. In our analogy, it's the lemon juice.
This is what dissolves another substance to form a solution. In our analogy, it's the water.