A non-essential amino acid (the building blocks of skin proteins, like collagen or elastin), that the body can produce itself, but its production decreases with age. When you put it all over your face, it works as a moisturizer and maybe more. 

According to great skincare blog Futurederm, glycine might help with wound healing and tissue repair and when used together with other amino acids, leucine and proline it might improve wrinkles

BTW, it's also a building block of a bunch of important and famous peptides, including copper-tripeptide-1, palmitoyl tripeptide-1 or palmitoyl hexapeptide-12.

Products with Glycine

Cellex-C Advanced-C Serum Nacific Glow Intensive Bubble Toner Paula's Choice Hydralight One Step Cleanser Kikumasamune Skin Care Essence Nu Skin Napca Moisture Mist The Ordinary Marine Hyaluronics Ausceuticals Peptide Moisturiser Joelle Ciocco Lotion Aromatique/Botanical Lotion Kiku-masamune Sake Emulsion Nature Republic Fresh Green Tea 80 Cream Olay Quench Daily Body Lotion Esho Drench Sebamed Frische Dusche The Ordinary Amino Acids + B5 The Ordinary Natural Moisturizing Factors + Ha Boo Bamboo Bamboo Fiber Charcoal Sheet Mask Leaders Insolution Mediu Amino Pore-Tight Mask Murad Eye Lift Firming Treatment™ Abnomaly Petrowhat? Bali Abnomaly Petrowhat? Baobab Abnomaly Petrowhat? Milk Abnomaly Petrowhat? Rio Avene Xeracalm A.D. Lipid-Replenishing Cream Dermalogica Map-15 Regenerator Isntree Real Rose Calming Mask Neostrata Skin Active Firming Collagen Booster Dr. Dennis Gross Skincare C + Collagen Brighten & Firm Vitamin C Serum Equal Beauty Super Serum Hydrantioxidant™ Eucerin Sun Fluid Sensitive Protect Spf 50+ Goodal Nature Ampoule Mask Firming LANEIGE Perfect Renew Regenerator Mediheal N.M.F Aquaring Ampoule Mask IOPE Hyaluronic Emulsion Leaders Mediu Amino Mousture Mask Lierac Paris Hydragenist Moisturizing Oxygenating Replumping Morning Mist Loopha Broadleaf Forest Body Wash Sativa 15 Revitalizing Eye Cream After Makeup Sebamed Flüssig Wasch-Emulsion The Ordinary Buffet The Ordinary Glycolic Acid 7% Toning Solution Hooray for Brallywood Butta The Ordinary Buffet + Copper Peptides 1% Avene Xeracalm A.D Lipid-Replenishing Cleansing Oil Biologique Recherche Serum Pigm 400 Dr. Dennis Gross Skincare C + Collagen Deep Cream Ishizawa Mochitto Awadate-Irazu (Face Wash Without Bubbling) NIOD Survival 0 Nakeup Face Ac Herb Mask Foam Sonia Roselli Japanese Cleansing Oil Zelens Z Balance Prebiotic & Probiotic Facial Mist