CRF150 - nothing.
CRF150F - Brazilian manufactured 150cc air-cooled 2-valve bike with steel frame and 1980's suspension technology. Weighs as much as a full sized enduro bike, built like a tank and as durable. IIRC, about 8 horsepower.
CRF150R - Mini MX bike, as in "Scaled down CRF250R". 17" front/14" rear wheels, aluminum perimeter frame, modern suspension and 4-valve liquid cooled engine.
CRF150RE - Same as the "R" version, but "E" stands for expert and gets you 19" front/17" rear wheels and more travel.
Honda did not ever make a 150cc 2-stroke production bike that I'm aware of. KTM may be the only one. Anyway, I know this info because I studied the crap out of it before buying my wife her first bike: 2003 CRF150F
She's since moved on to a CRF250X that is modified a bit.