See: Ubuntu 18.04 LTS
TLDR: Ubuntu 18 refers to the releases of the Ubuntu operating system from 2018, including the long-term support version Ubuntu 18.04 LTS (Bionic Beaver). These releases focused on enhancing usability, modernizing the desktop environment, and improving hardware support. Ubuntu 18 introduced updates such as the adoption of GNOME as the default desktop environment and deeper integration with cloud and containerization technologies.
https://en.wikipedia.org/wiki/Ubuntu_version_history
The flagship release, Ubuntu 18.04 LTS, featured the Linux Kernel 4.15, providing better support for modern CPUs, GPUs, and power management technologies. The transition to GNOME 3.28 from Unity offered users a refined desktop experience with improved customization options. For developers and enterprises, features like Snap package support, enhanced security with AppArmor, and compatibility with Docker and Kubernetes made Ubuntu 18 a powerful platform for scalable and secure applications.
https://ubuntu.com/blog/whats-new-in-ubuntu-18-04-lts
In addition to its desktop enhancements, Ubuntu 18 focused on cloud and server capabilities. It included native support for OpenStack Queens, streamlined virtualization options, and advanced management tools like Livepatch, which allowed for kernel updates without reboots. With its blend of stability, performance, and modern features, Ubuntu 18 catered to diverse user needs, from everyday computing to enterprise-level deployments.