Vitamin C is known for its strong antioxidant activity. It helps to slow down aging processes. The other positive effect of this ingredient is that it helps to make skin tone even. It's a great ingredient to counter dark areas and uneven skin tone. It's well-researched and considered safe. But it's acid and can irritate the skin if used too often.
Silica is used for improving texture of the product. It helps the product to spread out evenly. Very often it’s used in different exfoliants as an abrasive. It's safe and non-toxic.
Fragrance is a mix of chemical ingredients (usually 20-30 chemicals but up to 200 sometimes) that help the product to smell better. It can hide many bad things. Synthetic fragrances may contain many different chemicals, but manufacturers don’t want to reveal each of them for some reason and hide them behind the word "Fragrance".