Question

An electrolytic cell differs from a voltaic cell because an electrolytic cell

Answer 1

The answer would be: requires an outside energy source for a nonspontaneous chemical reaction to occur

An electrolytic cell is a cell that could change electric energy into chemical energy. It uses electric to induce a nonspontaneous chemical reaction. 
Electrolytic cells are the opposite of voltaic cells which will cause a spontaneous chemical reaction that produces electricity. 

Answer 2

The answer is because electrolytic cell requires an outside energy source for a non spontaneous chemical reaction to occur. Electrolytic cells require an input of electrical energy to cause oxidation-reduction reaction while voltaic cell is an electrochemical cell that uses a chemical reaction to produce electrical energy.