In Chemistry, a solvent is a substance (usually liquid) able to solubilizes other substances without reacting with (or against) them.

Solvents are usually classified as polar or non-polar according to their polarity (whether they are organic or inorganic).

The polarity of a molecule depends on several elements. Trying to simplify, we could generally say that all symmetric molecules are non-polar while all asymmetrical molecules are polar.

The polarity of a solvent shall define the kind of compounds the solvent can dissolve, as well as the nature of the other solvents and/or liquids with which it can be blended.

Polar solvents normally dissolve polar compounds better, just like non-polar solvents act more easily on non-polar compounds.

Water, since it is a very polar solvent, dissolves hydrophilic substances more easily.