There are three modes of editing on Google Docs, editing, suggesting and viewing.
Editing Mode: Allows you to edit documents directly.
Suggesting Mode: Any edits that you make in this mode show up as suggestions. Basically tracks your changes.
Viewing Mode: Use for reading and printing documents.
If you want to change which mode you are using there are two ways to do this.
The first is to go, below the comments and share buttons in the upper right corner, and select the Mode button. Choose the mode that best suits your need.
The second method is to select View on the taskbar, and then Mode. Choose the mode that best suits your needs.