I basically want to do what you see in the picture:

I read, somewhere on the Internet, that you can render the fbo and pass that fbo as a texture to render into the ImGui window. The problem is that I don't even know what an FBO is, and how to create it. I just want to have the scene rendered into my ImGui window (something like the scene window in Unity)

I'm asking for something like protocode, or something like that.

How can I render an OpeGL scene into an ImGui window?