Ok, now is pretty much clear.Every module could be deployed based on a Tomcat App Server.
However when I run the project in Idea I saw that a Jetty server starts. What is the story with this server?
We run Jetty in IDEA to serve some CUBA Studio plugin internal processes, it doesn’t rely to application deployment.
But we use Jetty when you deploy the app as an UberJar - runnable Jar file that does not need to be deployed to Tomcat or other app server. In fact, every UberJar has a Jetty app server packed into it and CUBA app is deployed to Jetty.