i don't put on make up that much

a concealor is used to hide blemishes and undereye circles, its very different then a foundation. you can use it as a foundation but its will be thicker and look a little weird. never use a pure concealor example pure green for pimples, mix it with your foundation and orange tinted comcealors are used for the blue circles under your eyes.

Covers up blemishes, pimples, and any other stuuf on your face. They usually have it in a powder or a liquid and you just dab some on your face.
Good Luck!

Concealer is a Soft Creamy, Pale Yellow base that will brighten your eyelids, and will tone down redness.
Brightens and lightens dark areas, erases spots, evens-out skin tones. Makes skin flaw-free

Concealer is usually used to cover imperfections such as blemishes, scars, bruises, and dark undereye circles. There are lots of different types as well; some are in liquid form and some are in a stick that you can just rub onto the imperfection. They're very helpful, esp. for undereye circles.

Makeup Tips --
Tips for applying Concealer
http://blog.360.yahoo.com/blog-gnA4Lmo_b7TZZTuzQA--?cq=1&p=9

concealer is a cream that is usually in a lipstick like forn that goes under the eyes to reduce dark circles or wherever you need to even out your skin tone. or to hide a pimple or mark