What are fluids?

Fluids is a substance that can flow (A fluid is a substance that can flow or continually deforms under applied shear stress).  It is usually classified as liquids or gases or Plasma. A liquid has intermolecular forces that hold it together so that it possesses volume but no definite shape.

A potion is a liquid ” that is supposed to have unique/magical properties.” But what are liquids?

A liquid is made up of tiny vibrating particles of matter, such as atoms, held together by intermolecular bonds. Like a gas, a liquid is able to flow and take the shape of a container. Most liquids resist compression, although others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container and maintains a fairly constant density. A distinctive property of the liquid state is surface tension, leading to wetting phenomena. Water is, by far, the most common liquid on Earth.

The density is another property of a liquid that is usually less than that of a solid, and much higher than in a gas. Therefore, liquid and solid are both termed condensed matter. On the other hand, as liquids and gases share the ability to flow, they are both called fluids. Viscosity is the property that decides the runniness of the fluids.