The common cold is a self-limited viral infection of the upper respiratory tract that causes symptoms like cough, sore throat, runny nose, and sneezing. It is highly contagious and can be transmitted through direct contact or inhaling airborne viruses. While usually mild and self-limiting, the common cold poses risks like pneumonia, bronchitis, and sinusitis if not prevented. Prevention methods include frequent hand washing, covering coughs and sneezes, vaccinations, rest, hydration, vitamin C, and avoiding smoking or sharing utensils.