Bids of 2D, 2H and 2S areshowing a 6-card suit and 12-15 HCP, as well as NO side four card major, nor any two singletons or voids. Intermedaite 3-bids show the same point strength, but require 7 cards.
2C is an artificial bids showing a very strong hand. Many players reserve 2D as another type
of artificial bids (e.g., Multi-2D, Mini-Roman).