why we should use hair conditioner

Most of us normally use shampoo's to clean our hair
and inturn most shampoos use some harmful substances in it,which makes our hair dry and loosen in strength.

in order to maintain its strength and look shine we need to apply hair contioner,which strengths fibre in deep roots of hair and most of conditioner uses fruit acids, vitamin B3 , fructose and glucose which smoothes hair to tip.

jigyasa wrote The most important reason to use conditioners is to help our hair regain the moisture that cleaning with shampoos take away. The important oils and moisture of our scalp and hair get lost in out day to day lives. Conditioners help replenish these.

Which conditioners would you recommend them? They all seem to be "best care for your hair"

Should you stick with one or vary it regularly?