Chronic is a strain of cannabis, a good yeilder, with a fairly good high, although every time its mentioned on this site it doesnt mean the strain. People use it as a slang for good weed.

Regs is regular weed, i presume.

mids is middle class weed

Dank is very good weed

dro is normally slang for good weed, but it actually refers to hydroponic growing

swchagg is dirt weed

All these words seem to only be an American thing. Took me a while to learn em all.