Dissolution is the dissociation or intermolecular occupation of a solute species in a solvent species to form a solution. A common dissolution process is the introduction of table salt crystals to water to form a saline water solution.
A general rule of dissolution is that "like dissolves like." Substances must possess similar intermolecular forces for them to be able to dissolve in one another. Introducing a solute to a solvent must involve some interaction between the two species for a solution to form.
For a solid solute dissolving in a liquid solvent, the interactions between the molecules of the solute and the solvent must be stronger than the interactions in between the solvent molecules. The stronger these interactions are, the faster the solute dissolves in the solvent and the larger the amount of solute that the same amount of solvent is able to dissolve.
An example is the dissolution of strongly ionic salts in polar solvents, such as water. Water molecules are able to separate the solute molecules into individual ions and surround them to form a solution. This mechanism of surrounding the solute molecules with solvent molecules is called solvation and must occur regardless of the phases involved for a solution to form.