If you have both a MacBook and an iMac, you can use the iMac as a display for the MacBook, or use an iMac as a display for another iMac. This gives you a bigger screen without needing to buy another screen.
Target Display Mode
It’s called Target Display Mode, and it’s easy to start using. Apple has a support page about this, with system requirements and display options. I’ll provide the short version here.
- A Mac notebook or desktop with a Mini DisplayPort or Thunderbolt port. If your Mac has Thunderbolt 3 (USB-C) ports, you can connect it using the Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter.
- A Thunderbolt cable or a Mini DisplayPort to Mini DisplayPort cable
- A supported iMac with OS X v10.6.1 or later
Entering Target Display Mode
- Turn on your iMac, and make sure the other Mac is logged in.
- Connect the Mini DisplayPort or Thunderbolt cable between the two computers.
- Press Command + F2 on the keyboard of the iMac that you want to use as a display.
Your target iMac will now display the desktop of the other, connected Mac. To exit TDM, just press Command + F2 again. It will also exit if you disconnect the cable or shut down/sleep the other Mac.