Online Blackboard, Google Jamboard

Google Jamboard is blackboard but online. Just like a blackboard, you can write, draw, or place sticky notes on it and the students who were invited via a link will observe changes in real time. Students can also be made editors and be allowed to make changes on the board as they wish.

Unlike a blackboard, Jamboard has undo and redo options that you can use to take back and repeat your changes. Additionally, it has a select tool which you can use to move the selected elements around. It also has a laser tool which you can use to highlight certain parts of your board for a short amount of time.