Services
Most services are optional: valet.sh only installs a small, essential baseline on every machine, everything else you install and uninstall yourself as needed, via install and uninstall.
The data services (MySQL, MariaDB, Elasticsearch, OpenSearch, Redis, Valkey, RabbitMQ, Mailpit) run in containers - Apple Containers on macOS, Podman with systemd user units on Ubuntu. Nginx, PHP, dnsmasq, Composer, NodeJS and Magerun still run natively. If you are coming from 2.x, see Upgrade from 2.x to 3.x.
Essential (always installed)
Optional (install on demand)
Note
A project's .valet-sh.yml can still declare which service versions it needs - init-instance will install any of them automatically if they aren't installed yet. This applies to all project types (Magento2, AEM, Neos), though it may not yet be implemented for every one of them.