Welcome!
Welcome to the Jena tutorial. Jena is a collection of tools and Java libraries to help software application developers and researchers to create semantic web applictions. By "semantic web" we specifically mean RDF, RDFS, OWL and SPARQL. This tutorial collects together a variety of material to introduce you to Jena programming. You don't need to know much background material to get started, but we will assume you know basic Java programming. There are some units that don't require you to be a programmer, but Jena is really a tool aimed at software application developers. It's fine to be learning Java at the same time as learning Jena, but this tutorial won't explain Java programming to you.
So how is this tutorial organised?
"The" Jena tutorial is a bit of a misnomer really. There are lots of tutorials here! We've organised the material as a collection of short units, and tried to make each individual unit reasonably self-contained. Collections of units are arranged as trails, where the units follow-on logically from each other. However, you don't have to stick to the trails. Each unit points out other related units, by topic or by other related trails, so you can jump around and follow what seems interesting. Incidentally, we've used RDF itself to organise the units, if you're interested in how we developed the tutorial see this unit.