Here is a selection of tutorials that will help you become familiar with some details of the EFL modules and APIs. You can approach them in any order, make sure you are familiar with the Getting started with EFL guide first.
Elementary is about displaying its widgets in a nice layout, for this purpose it provides a number of containers.
See too :
Once efl installed, you can see widgets in action by running elementary_test program, and corresponding code examples in https://git.enlightenment.org/core/efl.git/tree/src/bin/elementary