The three letter code for Kodak's T-Max 400 film. It is a modern black and white film. It is available in 35 mm, 120 and 220 roll film sizes, as well as in sheet format for large format photography.
T-Max 400 has remarkably small grain when developed properly. It reproduces skin tones nicely, and is therefore quite popular as a portrait film.
It's my favorite black and white film.