Google Docs is a free, Web-based word processor, spreadsheet, and presentation application .It allows users to create and edit documents online while collaborating in real-time with other users.
Documents, spreadsheets, and presentations can be created within the application itself, imported through the web interface, or sent via email. They can also be saved to the user’s computer in a variety of formats. By default, they are saved to Google’s servers. Open documents are automatically saved to prevent data loss, and a full revision history is automatically kept. Collaboration between users is also a feature of Google Docs. Documents can be shared, opened, and edited by multiple users at the same time. In the case of spreadsheets, users can be notified of changes to any specified regions via e-mail. Just enter the email addresses of the people with whom you want to share a given document and send them an invitation. Anyone you’ve invited to either edit or view your document, spreadsheet or presentation can access it as soon as they sign in.
Google Docs accepts most popular file formats including, DOC, XLS, ODT, ODS, RTF, CSV, PPT, etc. It also includes support for the Open Document format. It is also possible to upload and share PDF files.
You can access Google doc through your Gmail account.