Chromium is an open-source web browser, also the core of many popular browsers like Google Chrome, Brave, Vivaldi and even Microsoft Edge. There are people actually using Chromium in their day to day works, since it's the only way to experience the bleeding edge features of the core.
Mozilla Firefox is the default web browser for many Linux distros since it's fully open source, there are also several AUR (Arch User Repository) packages for different versions of Firefox for Arch based Linux. To install them is quite easy, either install with pacman directly or using AUR helpers like yay.
Brave is a open source web browser based on Chromium. It grows fast in the past couple of years, probably has something to do with its cryptocurrency Basic Attention Token (BAT). BAT has been integrated into Brave browser and allows users to earn it by browsing ads, or gives it to the content creator as tips.
In this guide we'll take Google Chrome (google-chrome) for example, showing you two ways to install packages from AUR. Including using the default package manager pacman and an easier approach with the AUR helper yay.