Here's a breakdown of the main components:

* Nitrogen (N2): About 78% of the air we breathe is nitrogen. It's essential for plant growth but isn't directly used by humans.

* Oxygen (O2): This makes up about 21% of the air and is vital for respiration in humans and animals.

* Argon (Ar): This inert gas makes up about 0.9% of the air.

* Carbon Dioxide (CO2): Though present in a smaller amount (about 0.04%), this gas plays a critical role in the Earth's climate and is produced through respiration and burning fossil fuels.

* Other Gases: Air also contains trace amounts of other gases like neon, helium, methane, and krypton.

While the composition of air can slightly vary depending on location and altitude, it's primarily a mixture of these gases.