Justin Tadlock: Beyond Prefixing: A WordPress Developer’s Guide to PHP Namespaces (WP Tavern)
Prefixing is one form of “namespacing,” which is just a fancy way of saying that names in this space belong to a specific project. However, prefixing (and suffixing, which is less common) is a hack from a time when no solution existed for the PHP language.
PHP 5.3 introduced an official method of namespacing, so the standard has existed for years. Because WordPress 5.2 bumped the minimum PHP requirement to 5.6, it is time for developers to shed their old habits and catch up to the rest of the PHP world.