Task notes are a great way to keep communication about the work in context and enable more effective asynchronous coordination amongst the team (and save on A LOT of emails and meetings).
Importantly, you can tag other users in a task note so that they get an 'in app' notification (notification bell in the top right of the screen) about the task note, and you can save links to the things you want them to look at in relation to the task note.
Open a task by clicking on the task name.
Scroll down and click on 'add note'.
You can format the text:
Bold
Italic
Plain text
Links
Headings
Lists
Checklists
and use the '@' symbol to tag other users so that they get notified about the task note (notification appears in the app in the top right of the screen - see the notification bell).