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 integrated into the motherboard or exist as separate expansion cards. Most sound cards support various audio formats and can enhance sound quality through features like surround sound and audio effects. They often include ports for connecting microphones, speakers, and other audio devices, making them essential for activities like gaming, music production, and video conferencing.