A useful report answers who, what, when, and where. Moderators are not in every channel at once; your job is to hand them enough facts to understand the situation without playing detective.
Include user IDs for everyone involved, not just display names. Note the channel and paste a message link if you can. Give an approximate time with your timezone. Describe what happened in plain language — quotes help more than labels like "they were toxic."
Think about proportionality. A rude joke and a credible threat deserve different responses. Report facts; let staff choose enforcement. Do not demand a specific punishment, coordinate pile-ons, or encourage others to harass the person you reported.
For what to attach and how to capture it properly, read our guide on gathering solid evidence. Weak or misleading evidence slows everyone down and can backfire if you are reporting in bad faith.