Among the main updates: modern interface with customizable themes, chat media gallery, view missed events in own notification panel, easy and fast way to send files up to 300 MB. A full list of the new features is posted on the Skype blog.
If you’re using Skype for Mac, Windows 10 November Update (2016) and lower, Windows 8, Windows 7, or Linux and have automatic updates enabled, the update will be delivered when it’s ready. You can download the new version from the official site.