Fine grain and great contrast so this is perfect for landscapes. That's it really. Oh and it has a nice coloured logo.
Ilford have a little more to say about it:
ILFORD DELTA 100 PROFESSIONAL is a medium speed, black & white film that uses our latest Core-shell™ emulsion technology to deliver superb image quality and maximum sharpness.
Excelling in scenes that are detail rich, its exceptionally fine grain makes DELTA 100 the perfect choice for many applications or genres. Showing outstanding quality at its recommended rating of ISO 100/21°, DELTA 100 will also produce stunning results rated between ISO 50 and 200.
DELTA 100 can be processed in a wide range of different developers using spiral tanks, deep tanks and automatic processors.