Domain Adaptive Object Detection

I’m planning to work on the research topic - Domain Adaptive Object Detection. Are there any pre-requisite topics to learn and understand before I dive into this area? I read some research papers regarding the same but understood nearly nothing.
I’m currently in the 3rd course of DLS specialisation.
I’m also aware that I should have a strong research question but at the moment I do not understand what domain adaptation is and how to apply unsupervised learning for the same!
Can someone please guide me on how to go about writing a research paper on this topic?