What distinguishes galvanic cells from electrolytic cells?

The distinction between galvanic cells and electrolytic cells primarily lies in the nature of the reactions they facilitate. Galvanic cells, also known as voltaic cells, operate on spontaneous chemical reactions to generate electrical energy. In these cells, the reaction occurs naturally without the need for an external power source; instead, the chemical potential energy is converted into electrical energy as electrons flow through the external circuit from the anode to the cathode.

In contrast, electrolytic cells require an external voltage to drive non-spontaneous reactions. These cells are typically used to facilitate processes like electrolysis, where an external source of energy is needed to induce a chemical change, allowing for applications such as electroplating or the decomposition of compounds.

Considering this context, the correct answer indicates that galvanic cells facilitate spontaneous reactions, which is a fundamental principle of how they operate and what differentiates them from electrolytic cells.