There are 5 different types of extinguishers, and each type is meant for different fire sources:
Class A - Uses water or water mist to extinguish wood, paper, cloth, and other common material fires
Class B - Uses special chemicals to put out gasoline, oil, and alcohol fires
Class C - Uses special chemicals to put out electrical fires
Class D - Commercial-grade extinguishers which use a dry chemical to put out combustible metals like magnesium and potassium. These are usually only found in industrial applications like machine shops and mining operations
Class K - Uses an expanding foam or other smothering agent to extinguish grease fires. This is the most commonly used extinguisher type for kitchens, both residential and commercial
It's extremely important to make sure that you have the correct extinguisher type for your home, since the wrong one won't put out the fire efficiently. If you want to keep a few on hand in your home and garage, the most common type you'll find is an ABC combination, though you'll also be able to find ABC/K for kitchens.