Arch Linux is a lightweight Linux distribution that prioritizes user control, simplicity, and novelty (in the sense of using the most current versions of most packages).
Probably the defining features of Arch are its minimalism and its trust of users. A fresh install of Arch comes with a command line, and it is up to the user to install and configure the software he wants on the system. This “DIY” approach allows users to create a system that meets their needs and doesn’t contain any software that they don’t want or need.
Arch Wiki
The Arch WIki is famously thorough and (supposedly) contains everything you need to know to install and maintain your Arch machine.
Opinion
I use Omarchy, but I’ve never actually tried “vanilla” Arch on a PC. I’m interested in trying it out on an old/small pc, though.