So, basically, Airplane Mode is a setting on your Mac that blocks all wireless connections, including Wi-Fi and Bluetooth. This means you can't browse the internet, check your email, or send messages, but you can still use all your offline apps like Word, Excel, and even some games!
When you enable Airplane Mode, you'll notice that your Mac's Wi-Fi and Bluetooth icons will disappear from the menu bar. Don't worry, it's not a bug - it's just your Mac's way of telling you that you're offline!