The redesigned Google Contacts web app has been in development since 2015, and it was recently updated to match Gmail's new look (thanks Edric and Wyatt). You've always been able to use the older version if you wanted, but that option is going away soon — Google has said the new Contacts web app will entirely replace the old version by February 2019.
The announced timeline specifically applies to G Suite users, but it's likely that regular Gmail accounts will follow the same pattern. On November 28, the new Contacts web app will become available to all G Suite users (or it can be force-enabled by the organization admin). On January 15, 2019, the new app will become the default, and admins will not be able to turn it off. Finally, the option for the old app will go away entirely on February 12, 2019.
The old Google Contacts web app
The updated Contacts site has been the default for Gmail accounts for some time now, so most people won't even notice this change. Still, there are undoubtedly a few people left using the old version who might not like change.
- G Suite