Why moisturiser is actually..

why moisturiser is actually used for ?if we use it does our skin become more oily, can it be used for oily skin

Moisturizers are used to lock moisture into the skin, by creating an occlusive barrier to prevent water loss. Some other moisturizers called humectants, hydrate the skin by pulling moisture from the air into the skin.

Moisturizres can be used for oily skin, but it is best to use the latter type, so that you are not blocking the pores, something lightweight and non-greasy. Look out for non-comodegenic labels, as this is what you want. HTH : )

its used to morsturize ur skin i have no clue why it is used but it is!

I'm assuming you mean for face. Using face lotions help make the face look smoother when makeup is applied and help it go on more sheer.

If using the right face lotion, it doesn't make your face oily. It will simply add more moisture.

Oily skin can use moisturizer, but it has to be an oil free kind with usually a drying agent like Salycilic acid to take away oil as well as moisturize skin.

Also, some moisturizer contains sunscreen, taking away nasty wrinkles.

Wikipedia says:

Moisturizers or moisturisers are complex mixtures of chemical agents specially designed to make the external layers of the skin (epidermis) softer and more pliable, by increasing its hydration (water content). Naturally occurring skin lipids and sterols as well as artificial or natural oils, humectants, emollients, lubricants, etc. may be part of the composition of commercial skin moisturizers. They usually are available as commercial products for cosmetic and therapeutic uses, but can also be prepared at home using common pharmacy ingredients.