All skin types can use it, oily skin can use it in lieu of a moisturiser & dry skin can use it mixed into the moisturiser.
Being a highly powerful moisturizer, which is also non-oily, it works on any skin type giving the necessary hydration. Depending on your need you can use up to 2% Hyaluronic acid on your skin on a daily basis in lieu of a moisturizer.
It can be used both morning and evening, before sunscreen, just like any moisturizer.
It can come in a cleanser/ water serum base, though serum has more concentrate of Hyaluronic acid and works better. You can use the serum as-is on a damp skin, or mix it with other actives or use in the place of a toner or mix it with moisturizer (in case of very dry skin).