One of the most wonderful things about cooking is the wide variety of textures, smells, and flavors you can impart in your food by using different ingredients. One very versatile ingredient is cooking oil. When people think of cooking oil, many conjure up an image of Wesson corn oil, or plain old vegetable oil. However, there exists a huge variety of oils of different types and flavors out there, from avocado oil, to white truffle oil. These can be used in your cooking to add a distinctive flavor, and to make sure different types of foods are cooked just the right way (for instance, peanut oil has a very high burning point, and is thus great for deep-frying foods at high temperatures).
The only drawback to using so many oils is that your expensive oil collection can go bad if you don't use it. Oils will not only lose their flavor over time; they will also take on a bland, unattractive taste that will make them useless in cooking. Since this is the case, it is best to use oils as quickly as possible, and store oils you plan to keep in a cool, dark place, preferably in an air-tight container. Some oils may be kept in the refrigerator to prolong their taste (for instance, I often keep my highly-flavored oils in the refrigerator, such as sesame oil, and hazelnut oil). Check your oils periodically for rancidity, and throw them out if they lose their characteristic aromas and flavors.