Google Drive is great for group projects. One person creates a document/presentation/spreadsheet and he/she can share it with the other persons in the group so that they may all work on the file simultaneously from various locations.
I shared my document with Molly and then typed "This is a shared document" onto the page.
Where the black cursor is, is my location on the page.
Where the Pink cursor is, is where Molly is on the page. We can both type at the same time and add to each other's work.
This collaborative working looks similar in Presentation. Each person can be on a different slide or everyone can be on the same at once.
Short Cuts for Commenting:
PC: Control + Alt + M
Mac: Command + Option + M
Highlight the word or phrase you wish to comment on and use the appropriate shortcut. A box will pop up to the right of the text and here you can leave your comment for all shared persons to see.
What should you do now that someone has commented on your work?
You can respond to the comment by clicking on the comment box, typing your comment into the text box and clicking reply [circled in blue].
You can simply fix the issue that was brought up and click resolve [circled in red] to "delete" the comment.