A face primer is used to create a clean canvas for your skin. After you moisturize, apply a thin layer of a foundation primer and spread it onto every inch of your face with your fingers, focusing on the spots you put the most foundation. It will give your face a little bit of a clean, slippery texture. Not slimey, a slippery dry sensation. This preps your face, keeping it clean from the oil and toxins of the makeup. It keeps your makeup looking fresh all day, prevents cakiness, and gives the skin a protective mask.
You can also use color-correcting primers. If your skin is particularly blotchy and prone to redness, try a green primer. The green is opposite red on the color wheel- it will balance and cancel out the redness of your face.
Some good face primers: 1, 2, 3
Eye primers are a lot like face primers. They give eyeshadow and eyeliner staying power and a clean canvas that prevents creasing. Before eyeshadow, eyeliner or mascara, apply a thin coat of an eye primer (do *not* use a face primer- they are not interchangeable) and blend with your ring finger. Now you are free to apply eyeshadow and eyeliner galore.
I even use a matte, skin-colored eye primer on the days I don't wear eyeshadow, because it makes me look more awake, and cancels out any puffiness or veins I may have. It just gives a clean finish.
Some good eye primers: 1, 2, 3
Quick note- My next BTB will be on foundation. Because there isn't one right or wrong way to do foundation- I've asked the rest of the girls who apply foundation on a regular, daily basis, to share their routine! Enjoy, ladies!