Difference Between a Free Cancellation Flight & a Refundable Flight
A free cancellation flight allows you to cancel your flight for free, with no charges from the airline, but it doesn't necessarily entitle you to a refund. Although you're able to cancel your flight for free, you may not be given your money back.
A refundable flight entitles you to a refund on what you paid for your airline ticket, but you might be subject to a charge from the airline in order to process that refund.
If you purchase a refundable flight with free cancellation, you can cancel your flight for free up until the time of departure, with no charges from the airline and you'll receive a full refund.