Curves

Any line is a curve. Line can be straight or bended

Curves are formed by drawing without lifting the pen from the paper

Simple Curve

A curve which does not cross itself is a simple curve.

Here,

     (1) & (2) are simple curves

     (3) & (4) are not simple curves

Closed Curve

A curve which has no open ends is a closed curve

Here,

    (2) & (4) are closed curves

    (1) & (3) are not closed curves