The new TV app introduces a recommendation feature that offers customized show suggestions. There are also new sections for movies, shows, sports and children’s shows, in addition to a navigation bar. A Channels feature allows you to view content from a subscription channel such as HBO, Comedy Central, CBS and Starz.
Other new features of 12.3 include support for AirPlay 2 Smart TVs from third-party vendors such as Samsung, LG and Vizio. There are also a variety of smaller features and big fixes. You can get the update by going to Settings, General, Software updates on your iPhone or iPad.
Update: macOS 10.14.5 has also been released, with the primary new feature being AirPlay 2 Support.