If you make a analogy to a real whiteboard in meeting rooms those have usually 1-4 pens and a eraser. Once you have opened the Whiteboard tab, you can start to sketch into it using built-in tools: Black, Red, Green and Blue pens and of course the eraser is there as well.
Update: check also article part II of using Whiteboard in Teams meetings, How to use Microsoft Whiteboard with guests in Teams Meetings and How to: adding a Microsoft Whiteboard to a team channel as a tab All you need to do is to open the meeting chat and click on the Whiteboard tab, which has been added automatically by Teams. When you create a meeting you can access the Whiteboard even before the meeting has started. Are you aware that every Microsoft Teams meeting includes a Microsoft Whiteboard that you can use before, during and after the meeting?
