please explain attched question.

what is a sector?

thankyou ;)

Choose 1 sector out of 11 sectors and choose 4 cap companies (micro, s, m, 1) in that sector. what do their recent price history tell you about their stock'market polularity and perception of value in the stock market or how it affects its value. would you buy their stock ? why or why not? Briefly explain how dollar cost averaging works