head = refering to the cylinder head on the engine.
http://catalog.roversnorth.com/catal...r%20head13.jpg

long block = like stated is the block and the head complete minus the tranny.
http://www.revolutionaryperformance....ck%20photo.jpg

OBD = Is "on board diagnostics" version on cars previous to 1995.
OBD2 = All cars built since January 1, 1996 have OBD-II systems. Manufacturers started incorporating OBD-II in various models as early as 1994. Some early OBD-II cars were not 100% compliant.
here's a pic of the connector. where you plug in the scanner to pull codes and information from the car's computer.
http://www.revolutionaryperformance....ck%20photo.jpg


DIY = Do it yourself. When you want to know how you can perform tasks like making a custom grill insert...that would be a DIY.