A bulb is a device that produces light when electricity passes through it. The most common type is the incandescent bulb, which uses a thin wire called a filament that glows when heated. Other types include LED bulbs, which are energy-efficient and long-lasting, and fluorescent bulbs, which use gas to produce light. Bulbs come in various shapes and sizes, making them suitable for different lighting needs. They can be used in homes, offices, and outdoor spaces. The brightness of a bulb is measured in lumens, while its energy consumption is measured in watts, helping consumers choose the right bulb for their needs.