Acids

Salicylic Acid has many benefits including being anti-bacterial, anti-inflammatory, anti-acne, and exfoliating. It loosens dead skin cells to relieve clogged pores and blackheads, reduces bacterial growth on the skin surface and in oil glands.
Salicylic is best for people with oily and acne-prone skin but can also be a great option for people with normal/dry skin who have the occasional breakout. Salicylic acid can be effective in almost any form: spot gel, face wash, peels, creams, pads, etc. There are also foundations and concealers that contain salicylic acid which can reduce shine and treat acne throughout the day.

Hyaluronic Acid is humectant, meaning it helps skin attract and retain moisture. It helps to strengthen the barrier of the skin so that its softer, smoother and appears plumper. Hyaluronic acid boosts skin vitality and vibrance so it's the perfect anti-aging ingredient as well.

Sodium Hyaluronate is smaller than hyaluronic acid and is able to move more freely into the deeper layers of the skin. This is an advantage since sodium hyaluronate is a powerful humectant that attracts and holds on to water, making it the ultimate skin moisturizer. This helps to hydrate the skin and keep it moist.

Glycolic Acid is great for people with oily or acne-prone skin but its benefits can really be reaped by any user. All skins can benefit from the regular use of glycolic acid, as it is a very small molecule that gently dissolves dead skin. It is a more gentle option than an abrasive exfoliating scrub. Glycolic's exfoliating properties help with lightening dark spots, reducing fine lines, and smoothing skin's texture. It's effective in pretty much any form.

Lactic Acid is another exfoliating alpha hydroxy acid but it's even gentler than glycolic. It's derived from milk so it has a moisturizing element that the other exfoliating acids lack, perfect for those with sensitive skin who are still looking to reduce hyperpigmentation and reducing fine lines.

Ascorbic Acid is actually just vitamin C. Vitamin C/ascorbic acid is a wonderful antioxidant that reduces fine lines and fights free-radicals as well as acting as a brightening agent that fades dark spots. Ascorbic acid is great for all skin types.

Citric Acid is derived from citrus fruits and is also an antioxidant. It's best for those showing early signs of aging or with sun damage.

Mandelic Acid has the largest molecule of all the AHAs which allows it to penetrate skin slower and gentler than the others, making it perfect for those with sensitive skin.

Oleic Acid is a fatty acid found in oils. High-oleic oils include almond oil and olive oil among others; they create an extremely moisturizing seal on your skin but aren't right for most non-dry skinned people.

Tartaric Acid is found naturally in many plants and fruits, including grapes. It's great for people trying to smooth out the texture of their skin.