The new version of the Gmail app allows it to take full advantage of the larger bezel-free display of the iPhone X, doing away with the large black bars that were previously present at the top and bottom of the app.
With the new view, you can see an additional email when viewing your main inbox, and there is more room for reading and composing email messages. It also looks much nicer in general without the ugly black bars.
Today's update also introduces support for adding non-Google email accounts to the Gmail app via IMAP.
Google has been slowly updating its iOS apps with iPhone X support and has thus far updated Gmail, Google Maps, and its productivity apps like Google Docs, Google Sheets, and Google Slides.
Gmail for iOS can be downloaded from the App Store for free. [Direct Link]