What's a DIT?

A digital imaging technician (DIT) works in collaboration with a cinematographer on work flow, systemization, signal integrity and image manipulation, to achieve the highest image quality and creative goals of cinematography in the digital realm.[1]

A DIT's role is especially prevalent with the widespread use of HD technology, in assisting cinematographers normally used to film stock in achieving their desired look. They may also be in charge of transferring and managing the image data, replacing the traditional film loader position.

From Wikipedia

The role of a DIT (Digital Imaging Technician):

When you rent a RED One camera through Superkrush, you will have the option to hire a DIT, a RED expert to ensure your shoot will run smoothly and you get the most out of your RED One camera hire. Our on-set DIT is highly trained so your camera is set up correctly and your data is captured and backed-up securely, so that your post-production runs smoothly too.

From SUPERKRUSH

I personally like the term "DMT" (Data Management Technician) over DIT, but they are essentially the same thing.

Here's a cool post from REDUSER about the gear that most RED DIT's use.