Have you ever stood in front of a shelf lined with bottles or tins of olive oil, often with their beautifully antiquated graphics, and wondered what the differences were among them? The labels announce the contents with descriptors such as extra-virgin, light, frozen, and pure, among others, making you speculate as to which is the best, if they're really all that dissimilar, and if a single oil can fulfill all your needs. There are significant differences among the various oils, and depending on how you'll be using the oil, it's best to stock your pantry with a range of types.
There's a good, two-part rule of thumb for distinguishing among the oils and then knowing how to use them: The deeper the oil's color, the more intense the flavor; and the stronger the flavor of the dish you're cooking, the stronger you'll want the oil to be. The top-shelf olive oils are always extra-virgin, which means the best olives are used, and no heat is involved in the process (heat will affect the oil's flavor.) Extra-virgin oils are perfect as a dip for bread or as a dressing for pastas and salads. The intensity of flavor is also influenced by the region in which the oil originated; Greek olive oils are robust, so they work well with menus that feature strong-tasting ingredients such as lamb and sardines, while French olive oils tend toward milder flavors. Frozen oils, which are frozen immediately after they're pressed, are the most intensely flavored of the extra-virgin oils and are perfect for drizzling over vegetables.
Pure olive oils are extracted using heat (and sometimes chemical processes) and have a milder flavor that's good for sauteing and frying. As the olive oil heats in the pan, the flavor diminishes proportionately. Light olive oil, the mildest of the bunch, is extracted from whatever remains in the olives after the extra-virgin and pure oils are obtained. If you don't want to give the flavor of olives much prominence in your dish, light olive oil is a good choice.