Think of $CO_{2}$ like the glass of a greenhouse or the windows of a parked car in the sun; it allows sunlight to enter but prevents the trapped heat from escaping easily.

CHAM: Carbon dioxide, H2O (Water vapor), Aerosols/Methane.

Greenhouse gases absorb and emit infrared radiation, a process known as the greenhouse effect. Incoming solar radiation (shortwave) passes through the atmosphere to heat the Earth, which then re-radiates energy as longwave thermal radiation. $CO_{2}$ molecules trap this outgoing thermal energy by vibrating, effectively warming the lower atmosphere.

In competitive exams, always remember that $N_{2}$ and $O_{2}$ are NOT greenhouse gases because their homonuclear diatomic structure prevents them from absorbing infrared radiation.