WordPress changes all the time and updates appear several times a year, some of which change the interface and ways to use the app. Currently we are using WordPress 4.4 (Clifford) which was released December 8th 2015.
Read up on all the changes and see a preview video at WordPress.org
The WordPress team has made it better and better with each upgrade: simplify the layout of the Dashboard, and make the functionality of the software ever more sophisticated and capable.
One of the genius developments of Clifford is the addition of Responsive images which automatically adjust to the viewport on any device.
The other exciting development of this version is the brand new embeds feature which makes it easy to drop a post URL into the editor and see an instant embed preview, complete with the title, excerpt, and featured image if you’ve set one.
A excellent resource and reference for clients who want to edit and update the content on their site is the The Easy WordPress Guide updated and published for free regularly by Anthony Hortin. It is well-written, easy to understand and covers all the basic and more advanced features of WordPress. I recommend it to my clients. For a small additional fee, you may purchase an unbranded version.