It's important to know that while High Sierra was officially supported on many Macs from late 2009 onwards, the official upgrade paths from Apple have since moved on. However, third-party tools like the have been created to allow installation on many older, officially unsupported Mac models from 2008 and even earlier.
macOS High Sierra 10.13.1 brought several improvements and enhancements to the table, including: macos high sierra 10.13.1