A solute is a substance that is dissolved in a solvent. A solvent is a substance that dissolves a solute. In other words, a solute is the substance that is being dissolved, and the solvent is the substance doing the dissolving. The most common example of this is salt (solute) dissolved in water (solvent). The solute is the salt, and the solvent is the water. Other common solvents include alcohol, vinegar, and oil.
The amount of solute that can be dissolved in a solvent is determined by the solubility of the solute. The solubility of the solute is affected by temperature and pressure. As temperature and pressure increase, the solubility of the solute also increases. This means that more of the solute can be dissolved in the solvent. Conversely, as temperature and pressure decrease, the solubility of the solute decreases, and less of the solute can be dissolved in the solvent.