Here's why:

* "Like dissolves like": A common rule of thumb in chemistry is that substances with similar polarities tend to dissolve in each other. Water is a polar molecule, meaning it has a slightly positive end and a slightly negative end.

* Polar Solutes: Water readily dissolves polar substances like salts (e.g., sodium chloride), sugars (e.g., glucose), and many acids and bases. The polar ends of water molecules can form strong attractions (hydrogen bonds) with the polar ends of these solutes, pulling them apart and dissolving them.

* Non-polar Solutes: Water does not dissolve non-polar substances like oils, fats, and many organic compounds. These substances lack the charged regions that water molecules need to form strong attractions.

Examples:

* Salt dissolves in water: Salt is ionic, meaning it forms charged particles (ions). Water molecules surround these ions and pull them apart.

* Oil does not dissolve in water: Oil is non-polar and does not interact strongly with water molecules.

Therefore, water's ability to dissolve a substance depends on the substance's polarity and the strength of the interactions between water molecules and the solute molecules.