Publishing content automatically unlocks it; other authors will be free to make changes to that section (which will lock it to them).

Sometimes, you may not want to publish a section, but might want to unlock it so that another author can work on it. In this case, select the section in the left hand menu and use the 'Unlock' button.

The content will remain green (indicating it is not yet published, and is different to the live version), but the icon will revert to the document one.