Java Development Kit (JDK) is the engine that runs everything from JDeveloper to the application server. The latest version of the JDK is JDK 7u25 at the time of writing, but if you find a newer version, don't hesitate to use it instead.
You should download the latest JDK and it should work just fine, but you have to select the JDK suitable for your Operating System and its architecture
You will need an oracle account. This is also important when installing the Oracle Database and JDeveloper, so you should get one now if you don't already have one, and it's free too!
Depending on the operating system, the ...