Format: Format is a menu used to change the way a document looks and is organized, such as the font, font style (title, header, normal), font size, characteristics (bold, italics, underline), bullets, and line spacing.
Insert: Insert is a menu used to access special features such as images, drawings, tables, charts, and page numbers.
Tools: Tools is a menu with additional features that can be helpful such as spelling and grammar check, dictionary, translate, voice typing, and Explore.
note:
Viewer: A file-sharing permission you assign to a viewer with the link so they can only view the document, but cannot comment or edit
Commenter: A file-sharing permission you assign to a commenter with the link that can not only view the document but can also make add a comment to the document.
Editor: A file-sharing permission you assign to the editor with a link where they have full editing rights and can make changes to the file.