iMac as display monitor to macBook

No the M3 MacBook Air can not use the 2015 iMac as a display in Target Display Mode.

carefully read > Use your iMac as a display with target display mode - Apple Support

What you need, is an aftermarket external display for the MacBook Air.

see > Use an external display with your MacBook Air - Apple Support

Note that Luna Display has this interesting advisory on its support page:

To me, that says it is not suitable for making any iMac a main monitor for another computer.

The simplest, most efficient, and most cost-effective solution is still a traditional free-standing external monitor.

noamm050 wrote:

I have an iMac Late 2015 macOS Monterey version 12.7.4 with thunderbolt 2 and I want it to serve as a display monitor for my macBook Air M3 2024 macOS Sonoma 14.4.1 with thunderbolt 4. I also have a corsair tbt100 docking station plugged to the macBook and a thunderbolt 2 cable (that does not connect to the docking station). Can I display the macBook on the monitor of the iMac ? if possible how ?

You can't do it with Target Display Mode. Your Late 2015 iMac doesn't support it. On top of that, your M3 MacBook Air can't use ANY iMac as a Target Display.

There may be third-party workarounds such as Luna Display (Astropad) or Duet Display, but they're not the same as a Target Display connection or a hardware-supported connection to a real monitor.

Your Late 2015 iMac is also too old to be an AirPlay Receiver for AirPlay to Mac.