The letters on light bulbs can seem like a foreign language, but they're actually pretty simple to understand. The most common letter is E, which stands for Edison, the inventor of the light bulb. The next most common letter is A, which stands for American Standard. Other letters you might see are R for reflector, C for candelabra, and D for decorative.
Knowing what the letters mean can help you choose the right light bulb for your needs. If you need a bright light for reading or other tasks, look for an Edison bulb. If you want a softer light for general use, go with an American Standard bulb. And if you're looking for something special to spruce up your home décor, check out bulbs labeled as reflectors, candelabras, or decorative.