Soluble substances tend to dissolve in a solvent (usually water), to a significant extent, dissociating its components.
Insoluble substances do not dissolve in solvents to a significant extent, and sometimes in a reaction, we see an insoluble salt forming a precipitate, which is an insoluble solid at the bottom of the reaction
A solution is composed of two main components, a solute and a solvent, usually the solvent is the one that we have with more quantity, and solute we have in less amount.