You can already see what's changed in a file by reviewing the revision history in a Google Docs file, but now you can also do the same to two separate documents. Here's how to use the Compare Documents tool.

In a web browser, fire up the Google Docs home page and open up an already-existing document you want to compare.

Once the document loads, click Tools > Compare Documents to start running the comparison tool.

Click Tools > Compare Documents.

A small dialog box will appear, allowing you to select a second document to compare against the first one. Click "My Drive" to pull up the file picker.

Click "My Drive" to open a second file.

Navigate to the file you want to use, click it, and then select the "Open" button to choose the document.

Navigate to the file, click it, and then click "Open" to open the file.

The name you enter into "Attribute Differences To" will appear as the person who made the changes in the final document as an edit. Enter your name and click "Compare" to let Google work its magic.

Enter your name as you want it to appear in the comparison file and click "Compare."

When the tool finishes, click "Open" to open the comparison document.

When the comparison is ready, click "open" to open it.

The comparison document will open up as a third file with all the highlighted suggestions inside the body of the document and who made them on the right. In addition, you'll be able to see what changes were made and when.

The comparison will open in a new file, showing you all of the changes made between each document. On the side, each suggestion will appear as a comment that you can either accept or reject.

Each edit will appear as a suggestion that you'll have to accept or reject. You can decide to keep or dismiss an edit in the comments section on the right side of the document. Click either the checkmark or the "X" to accept or reject each one.

Accept or reject a suggestion from the right side.

Related: How to Add Comments in Google Docs

If you click the comment, you'll be able to reply to the suggestion and give insight as to why the change was made. When you share the file with others, replies will be viewable by anyone who has access to the document.

Enter a little more information as a reply to the comment.

After you follow up on all the changes made to the Google Docs document, you don't need to do anything else. The document automatically saves to your Drive in the root folder as "Comparison Of <File 1> & <File 2>" where

        <File 1>
    

and

        <File 2>
    

will be the names of your files.