Explain the role of solutions?

Solutions:  A solution consists of a liquid solvent plus substances dissolved in it, called solutes. Solutes may be ions, atoms, or small molecules, or combinations of these. Solutes are not changed chemically when they dissolve.

The concentration of a solution refers to the amount of solute dissolved in a certain amount of solvent. At some point, the solvent is no longer able to dissolve more solute; this is called the saturation point. For example, sugar crystallizes from a solution if it is oversaturated.
Most biological reactions occur in water, that is, in aqueous solutions.