broken charger

I understand your MacBook Air's power adapter is not charging your Mac.

• If the power adapter uses a USB-C "Thunderbolt" connector, you need to confirm you are using the correct power adapter and cable for it: Find the right power adapter and cable for your Mac notebook. Then, please read If your USB-C power adapter isn't charging your Mac notebook.
• If your MacBook Air is an older model that uses a power adapter with a MagSafe connector, please read Apple Portables: Troubleshooting MagSafe adapters.

Either way, if your Mac's battery is simply not charging, please read If your Mac battery won't charge - Apple Support.

Buy a new one from the Apple Store.

But, if your Mac is still under warranty or AppleCare, contact Apple since the charger is also covered.