For oily skin
You may have oily skin if sometimes it feels too greasy to wear moisturizer especially in the summer. Having much oiler skin in midday than in the morning (without using any products) and having large pores are also signs that your skin might be the oily type.
In most cases, the skin is producing too much oil because it is doing everything it can to retain water/hydration. The oil then serves to cover the skin with a protective layer so that hydration can no longer escape. So if you make sure that the skin is always supplied with enough hydration, the oil production regulates itself almost by itself.