WildFly, formerly called JBoss, is an application server, and WildFly Swarm is a project that deconstructs the application server into modular parts. Swarm is aimed towards microservice applications, allowing the putting together of just enough subsets of the Java EE features that are required by the application.
An easy way to get started is to use the project generator page to select the features, or fractions, as they are called in Swarm terminology, and generate a maven project.
You can head over to the following link: http://wildfly-swarm.io/generator/: