A mixture that forms when one substance dissolves in another is called a solution.

Here's a breakdown:

* Solution: A homogeneous mixture where one substance (the solute) is evenly distributed throughout another substance (the solvent).

* Solute: The substance that dissolves.

* Solvent: The substance that does the dissolving.

For example, when you add sugar to water, the sugar dissolves, and you get a sugar solution. The sugar is the solute, and the water is the solvent.