What does it mean when one substance dissolves in another?

Factors Affecting Solubility 

Temperature  

The solubility of a given solute in a given solvent depends on temperature. For many solids dissolved in liquid water, the solubility tends to increase with increasing temperature. When water molecules are heated they vibrate more intensely and are able to interact with solute molecules. 

The solubility of gases shows a different relationship to temperature compared to solids; this means that when the temperature increases the solubility of the gas tends to decrease. 

Pressure  

Pressure has a negligible effect on the solubility of solid and liquid solutes, but it has a strong effect on solutions with gaseous solutes. This can be clearly seen when opening a can of soda; the hissing of the can is due to its contents being under pressure, which ensures that the fizzy drink stays carbonated (that is, the carbon dioxide stays dissolved in the solution). The conclusion is that the solubility of gases tends to correlate with the increase in pressure. 

Sources

What are the differences between solubility and miscibility?. (2021). Retrieved May 30, 2021, from https://www.geniolandia.com/13092047/what-are-the-differences-between-solubility-and-miscibility

How Does Alcohol Dissolve Oil?. (2021). Retrieved May 30, 2021, from https://sciencing.com/info-12066577-alcohol-dissolve-oil.html

Solubility | Introduction to Chemistry. (2022). Retrieved 10 February 2022, from https://courses.lumenlearning.com/introchem/chapter/solubility/  

What is the Definition of Dissolve in Chemistry?. (2021). Retrieved 30 May 2021, from https://sciencing.com/what-is-the-definition-of-dissolve-in-chemistry-13712180.html