Most spokes are very thin and when they are put under a lot of tension, they can break. Spokes support the weight of the rider and transfer forces to the rim so they play an important role. They also help to maintain the round shape of the wheel and keep it in a straight line. Spokes flex and make a tinging noise as you ride. Some riders never get a broken spoke whilst others have a few a year. It depends on how and where you ride your bike.
You should check your spokes every time you get on your bike. When a spoke breaks, it’s paired spoke and all the spokes close to it will be vulnerable to breaking too because they will be under increased strain. Damaged spokes can cause punctures if they go into the outer wheel. A damaged spoke could also get caught in the other spokes and stop the wheel from turning which will make you fall off the bike! You can flick the spokes to find any that are broken. Some spokes do move around a lot and that does not necessarily mean that they are broken. Often, the spokes around them will be tight and this is done to keep the wheel true.
If you hear a spoke break, stop cycling and have a look at it. You must stop it from waving around so find something to tape it to the spoke next to it. If possible, push your bike to a location where it can be repaired. However, this is often not possible and spokes have a habit of breaking when you are miles from help! In this case, continue your ride but do so carefully. The wheel is in danger of buckling so go slow and avoid all holes and bumps. If you hit a bump at speed, you are very likely to break more spokes and get thrown off the bike!