model number question

i feel pretty dumb asking this, but what exactly are the differences between the e30's, etc. what exactly does the e stand for, and why are the models listed by these instead of their series number (328, 330, etc)? which models are which "e" numbers?

E12 is the 1978-1981 5-Series
E20 is the 1973-1974 2002 turbo
E21 is the 1976-1982 3-Series
E23 is the 1978-1986 7-Series
E24 is the 1976-1989 6-Series
E26 is the 1979-1980 M1
E28 is the 1982-1988 5-Series
E30 is the 1984-1991 3-Series
E31 is the 1990-? 8-Series
E32 is the 1987-1994 7-Series
E34 is the 1989-1995 5-Series
E36 is the 1992-1998 3-Series
E38 is the 1995-2001 7-Series
E39 is the 1996/7-2003 5-Series
E46 is the 1999-present 3-Series
E60 is the 2003-present 5-Series
E63 is the 2004-present 6-Series
E66 is the 2002-present 7-Series
E87 is the new 1-Series
E90 is the future 3-Series

"E" stands for Entwicklung, German for development

I know im missing some cars (Z3/4, X3, X5, some of the older 2002s)

thanks a lot. that answers my question completely. thank you.

Wasn't there E65 7-series before E66? E65 was the first generation, then the E66 is current with the newer additions to the car?