Using comments on Google Docs lets you connect with your teacher(s) and also helps when collaborating with others.
Using the comments feature while you are working on a doc is the best way to get feedback and ask questions BEFORE you turn in work (you can also use the class comments or private comments option in Google Classroom).
Highlight the text you wish to comment about.
Click the + button (Add comment)
Type your comment.
Click Comment
Highlight the text you wish to comment about.
Click the + button (Add comment)
Type @ symbol and the person's email address and then your comment.
Tick the box to assign the comment to that person.
Click Assign.
Clicking the speech bubble with lines (near the Share button in the top right hand corner of your doc) opens the comment history and shows you all of the comments made on the doc.
You can also add a comment to the doc from here.