Well this is not a mystery question anyways but if you are a beginner then this quick introduction should help.
Eyeliners come in liquid and gel forms that one can apply to enhance or highlight features of the eyes. Eyeliners are typically used to highlight the eyelids and/or to alter the contour of the eyes. These come in black and many other colours. These are also available in shimmer finish, that are typically applied on special occasions.
There are many eyeliners present in the market that are chemical based as well as organic ingredients based. It totally depends on your needs, pocket and preference as to what you choose.
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