A sound card is a hardware component in computers that enables the input and output of audio signals. It converts digital audio data into analog signals that can be played through speakers or headphones, and vice versa for recording. Sound cards can be built into the motherboard or installed as separate expansion cards. Modern sound cards often support various audio formats and can enhance sound quality through features like surround sound and audio effects. They are essential for activities such as gaming, music production, and video editing, providing a better audio experience than standard integrated audio solutions.