The vert.x documentation is organised into a few different manuals.
The install guide shows you how to install vert.x
The main manual contains an introduction to vert.x concepts and deals with general vert.x concepts that are independent from the specific programming language
If you're new to vert.x it's highly recommended you read this manual first.
The API manual goes into detail about everything you can do with the vert.x API.
There's a different version of the API manual for each supported language
We also provide javadoc/yardoc/groovydoc for the API
The modules manual tells you everything you need to know about using and creating vert.x modules.