What Were The Airbus A340-300E & A340-300 Enhanced?

When it comes to aircraft models and their naming, most of us are familiar with the main types and the main variants. For the now-out-of-production, four-engined Airbus A340 – the main variants were the -200, -300, -500, and -600. But do you know what the A340-300E and -300 Enhanced were about?