There are many types of masks each with a specific purpose and benefits.  In general, the purpose of a mask is to create a temporary barrier which results in increasing tissue and cellular activity, increase oxygen levels, and aid the skin to enhance its metabolism.  Masks are formulated to address different skin issues and conditions. 

Exfoliating Masks:  These usually contain enzymes or fruit acids.  Depending on the ingredients and time left on, they achieve various levels of skin resurfacing.  When dead hardened cells on the surface are removed, it is easier to clean out impactions in the pores and prevent future impactions.

Peel Off Masks:  Known for exfoliation, firming, or tightening of the skin.

Gel Masks:  Calm, sooth, and hydrate the skin.  Usually hyaluronic acid based and for normal to oily skin types.  Leave skin smoother and more even in texture.

Cream Masks:  Used for hydration and anti-aging in dry to normal skin types.

Rub Off Masks:  Exfoliates the skin by the movements used in removing the mask.

Skin Lightening Masks:  Usually contain botanicals such as licorice and bearberry to naturally lighten hyperpigmentation caused by sun damage.

Deep Cleansing Masks:  Usually contain clay or mud and are used to remove any cellular debris that may be clogging the pores and causing breakouts.  Many absorb excess oil and are beneficial for oily and acne prone skin.

Thermal Masks:  Create heat and help soften fine line and wrinkles as well as aid in penetration of specific serums applied below the mask.

Cryogenic or Cold Masks:  Used to tone and tighten the epidermis, calm inflammation, and reduce irritation after medical cosmetic procedures such as microdermabrasion, laser treatments, etc. 

 
Depending on your skin type, masks can be done at home once a week for 10-20 minutes.  Always follow the manufacturer directions.