Reeds are important to many woodwind instruments. One could say that without the saxophone or clarinet the great sounds of jazz may never had existed. Reeds are so important in bringing a unique sound to an ensemble.
There are different reeds to fit each instrument, and some instruments require two reeds to get the sound they make. You could never use a saxophone reed on a clarinet, or a clarinet reed on a bass clarinet, and an oboe and bassoon actually requires two reeds to work.
The way that the reed works is a symbiotic relationship with the mouthpiece. When you blow air into the mouthpiece with the reed attached it makes the air in the instrument vibrate and create acoustic waves. In order to maintain sound of your instrument your reed must remain in good condition.
The one and only problem with reeds is that they are incredibly delicate, they break and bend incredibly easy and they do not stand the test of time. When you play them, they wear out, and the temperature also plays a role in their lifespan as well.
When you first open up a box of reeds, they have been dry for a good deal of time, in order to soften them up and get them ready to play the best method is to moisten them in a cup of water for a few minutes or if you are just getting warmed up after you initially softened a reed, many people hold them in their mouths just for a minute or two to get them to a point where they are perfect to play.