To answer this; we need to define what the difference is between shampoo and conditioner.
Put simply; Shampoo is used to clean the hair. It removes the oils, dirt, skin particles, dandruff and that gradually build up in hair. Conditioner is designed to add moisture to the hair and scalp, soften the hair, increase shine and prevent tangling. Think of a hair conditioner as fabric softener for your hair.

Together they provide the best result, the shampoo cleaning the scalp and hair and then the conditioner improving and protecting the hair particle.

To work out the best combination, all you need is to find the correct products for your hair type and needs. Your groomer can do this for you every visit and it may vary depending on your hair health and the seasons.

How to apply shampoo and conditioner like a boss

Most shampoos can be used every day. In the shower, simply apply a small amount to the palm of your hand and rub hands together to distribute the product. Very gently massage the shampoo into the hair and scalp with your fingertips and rinse thoroughly with lukewarm water.

Most conditioners can be used every day. For maximum benefit, leave the conditioner on the hair for two minutes (this is a good time to shave your face) and be sure to rinse well with lukewarm water.

SHAMPOO
There are several common types of shampoo.

Because most men have hair that is less than three inches long, most “normal” shampoos will work for the average guy. When choosing a shampoo, select one that specifically targets problems you are having with your scalp — dryness, oiliness, etc.

Shampoos for oily hair contain cleansers designed to remove as much oil as possible. These are good for men with oily scalps, but may cause excessive dryness in men with a normal scalp.

Shampoos for dry hair like American Crew Daily Moisturising (often called moisturising shampoos) are specifically formulated to add moisture to the hair and scalp. Unless you have very dry hair, these types of shampoos are not necessary and can often weigh down normal hair.

Thickening shampoos like Anti-Dandruff & Sebum Control by American Crew (or volumizing shampoos) often contain glycerine, which helps the hair retain water and swells the hair strand by lifting the cuticle. The hair’s cuticle is a hard shingle-like layer that looks like fish scales under magnification. Under normal circumstances, these shingles lie flat. Many thickening shampoos cause the cuticle to open up, thus swelling the hair shaft. In this state, the hair is more vulnerable, so following up with a good conditioner is recommended.

Dandruff shampoos are formulated to help prevent the itching and flaking associated with dandruff. Before using a dandruff shampoo, make sure you really have dandruff. Dandruff (seborrheic dermatitis) causes thick flakes and irritated scalp. If you’re seeing smaller, fine white flakes, the problem is likely dry scalp which can be corrected with a moisturising shampoo and conditioner. Start by using a dandruff shampoo every other day (alternating with a good moisturising shampoo) as dandruff shampoos can often cause excessive dryness.

CONDITIONERS

Moisturising conditioners contain ingredients that help the hair retain moisture and should be used by those with dry, curly, or coarse hair. If your hair is extremely dry, use a conditioner that contains essential fatty acids. These EFA based conditioners contain oil similar to sebum, which the scalp naturally produces.

Thickening conditioners (or volumizing conditioners) coat the hair with a layer of protein with makes the hair appear thicker. This type of conditioner can help fill in the gaps left in the cuticle if it is damaged and add smoothness and shine to the hair. Thickening conditioners are suitable for those with fine, limp, or damaged hair.

Leave in conditioners work, much like a facial moisturiser, by nourishing your hair. These types of conditioners are not rinsed out and can also help add a bit of manageability to the hair as well as protecting it from the sun (look for one with a sunscreen). Many guys believe their hair behaves better the day after a shampoo and a leave in conditioner can give the same manageability while allowing you to shampoo every day.