What does 10% vitamin C actually mean in this serum?

The percentage refers to the concentration of a vitamin C derivative called sodium ascorbyl phosphate, not pure L-ascorbic acid. This derivative is water-soluble and stable in water-based formulas, which is why it can be used in a serum with the texture described here. In skin care, vitamin C is included for two reasons: it helps defend the skin from oxidative stress caused by UV exposure and pollution, and it plays a role in collagen formation. That is why products like this one are often chosen when the goal is a brighter-looking complexion, smoother skin and a firmer feel over time. The 10% figure tells you the amount of sodium ascorbyl phosphate in the formulation; it does not mean the same thing as 10% pure ascorbic acid, and the product information does not provide a direct equivalent. What matters more is how the formula behaves on your skin and where it sits in your routine. Because this is a stable derivative, it can be a practical option for someone who wants a vitamin C serum without the pH sensitivity that pure vitamin C often brings. The serum also contains pineapple extract, orange peel oil and glycerin, so the overall effect is not only from the vitamin C: pineapple extract adds a softening, revitalizing feel, orange peel oil adds an aromatic note, and glycerin helps the skin stay supple. If you have never used a vitamin C product, start slowly and follow the gradual introduction advice in the product instructions.