The Edit module allows you to edit the node content directly on the node view page. It works with CKEditor and also it will be included in the Drupal 8 core. So see how it works in Drupal 7 first.
1. Drupal 7 >= 7.22 is required.
2. Download and install the CKEditor and Edit modules.
3. Grant the Access in-place editing to the relevant roles.
4. Go to any node view page, you will find the Quick edit link on the sidebar.
5. Click the Quick edit link and you can edit the content on the fly.
Currently, the Edit module does not allow to edit the empty field. In other words, you can edit those fields which are not show on the node view page. This module is still under active development and i am sure it will be getting more and more mature in the near future.
Reference: Drupal Module – Edit