Really depends on what you're trying to do
Quarkus was made to make microservices very easy. When we're talking about microservices often REST web services are involved and they're deployed onto a cloud provider like AWS, Google Cloud, Microsoft Azure, etc. Quarkus also targets Kubernetes by creating native applications through GraalVM.
All of that aside, you don't have to use any of that if you don't want to. Quarkus will still work just fine on the regular JVM, and you can still write typical Java web based applications with it. I'd recommend understanding web services, ideally REST, and CDI to get started.
