WildFly, formerly known as JBoss AS (Application Server), is an open-source enterprise-level Java application server. It provides a platform to develop, deploy and manage Java-based applications and services. It supports various programming languages, frameworks, and platforms, including Java EE, Spring, RESTful web services, and more. WildFly offers high-performance, scalability, and security features, making it suitable for creating mission-critical, robust applications. It is maintained and supported by the open-source community and Red Hat.