Shampoo is used to clean hair (remove dirt and hair oil). Conditioner is used to restore moisture to dry hair. Conditioners also supposedly make the hair softer, easier to comb/brush out, and restore shine, body and pH balance to the hair.
Order in which to apply
Apply shampoo first to clean your hair. Apply conditioner only once the hair is clean.
Cleaning hair with shampoo can be done daily. Conditioners can be applied with less frequency (once every 2-3 days). People younger than 30 may not need conditioners as frequently as those over 30 because growth hormones release natural hair oils.
Shampoos are acidic and conditioners are basic.