Replacement bulbs are light sources designed to replace burnt-out or damaged bulbs in various fixtures. They come in different types, including incandescent, LED, and fluorescent, each offering unique benefits such as energy efficiency and longer lifespan. When selecting a replacement bulb, it's important to consider factors like wattage, brightness (measured in lumens), and the type of socket used in the fixture. Common applications for replacement bulbs include table lamps, ceiling lights, and outdoor lighting, ensuring that spaces remain well-lit and functional.