Pantheon is a hosting platform which offers a dedicated hosting environment for Drupal and WordPress, specifically.
Pantheon is a Platform as a Service (PAAS) and quite specialist hosting service, which can broadly be referred to as a managed WordPress host. As a consequence, it is dramatically superior – for WordPress – when compared to more generic one-size-fits-all shared hosting services.
There’s support for Git, automatic test, staging and production environments, making it a great environment for business grade WordPress – i.e. WooCommerce, or mission critical WordPress, particularly where developers are regularly working on the site.