It should include detailed bug reports, ideas, or any other sharing. Extra validity points will also go to participants with in-depth feedback and/or solutions & improvement strategies.
Upon entering the Ready Feedback chat, you'll see the full command list and instructions on how to leave feedback. Follow those guidelines and you'll stand a very good chance of winning (multiple) rewards.
It should be noted that “first come, first served” rule also applies here. Among those giving the same valid feedback, only the first one will be recognized. Thus, you should give feedback as much, early, and quality as possible!