Each page has page permissions. These can be accessed the Toolbar in 'Edit' --> 'Page Settings' --> 'Permissions'. You can either choose one of the quick standard options or you can customise the settings to your own needs by clicking 'Advanced'.
In 'Advanced', each column represents a different permission and the rows determine who gets that permission. 'View' means you can see the page, 'Edit' means you can modify or delete content. Remember, the site leader always has all permissions on every page.