Eyeliner is something that is optional when doing make up. It defines the eye more and make the lashes more full looking. Personally I like to wear eyeliner but some people look better without it. There are many forms of eyeliner. The first one is pencil. That come in a legit pencil form. You even have to sharpen it when it gets dull. Then there is gel. That comes in a little pot and you have to dip a brush in and draw it on your eyes. Then there is liquid. That probably the hardest way to do eyeliner but then done right it looks so good.
There are two way do do eyeliner. One is you can just draw on the upper lash line or two you can draw a wing. That elongates the eye and makes you look more awake. You can also put it on the bottom eye lash line to make the eye even more defined. I would only do that for a night time look though because it can be a little to dramatic.