Since slot machines are not usually interactive (once you set the betting parameters, the machine does everything for you), software studios want to introduce more features that go in this direction. The Respin feature from Microgaming is one of them. It’s available in some of their slots, such as Retro Reels and Reel Gems.
It’s a very common situation to get four our of five symbols of a winning combination in an active payline. You wish to spin the fifth reel to get another chance for the jackpot payout. This is what the Respin feature lets you do, but it’s an additional bet. It’s up to you to decide if it’s worth it or not.
The first spin in slot games with the Respin feature is a normal one. After that, the Respin button under each reel will display the amount you need to pay to spin this particular reel again, while keeping all the other reels fixed. The cost keeps changing as the chances of winning are different for each reel and in each spin.
You click the Respin button for the reel you want to spin again. The amount shown on the button gets debited from you account. Wins resulting from the respin will get paid out. The amount on the Respin button will change. You can repeat the process as many times as you want, as long as you pay every time.
Obviously it’s not required to ever use the Respin button. You can simply keep using only the Spin button for all the reels together.