You can use Bezier curves to draw complex lines and shapes. It is a very simple and intuitive process.
Structure of a Bezier curve.
1. Bezier curve. It is called a path and is a fundamental element. All other elements are intended only to give the desired shape to the path.
2. Anchor Points. Bézier curve is bounded by these points on two sides, they largely determine path's shape. If a path has more than two anchor points, then it consists of a set of Bezier curves. Anchor points can be moved relative to each other, adjusting the look of the path.
3. Guide line. This is a line coming out from an anchor point. It is a Bezier curve's tangent. Any changes made to the guide line will directly reflect on the appearance of the path.
4. Marker. The element that ends a guide line. Markers change the length and the position of guides. The length of the guide defines the amplitude of a curve, the degree of its "bulge".
Changing path using guides:
Figure A shows two Bezier curves in the form of a wedge. Markers 1 and 2 are the ends of guide lines between the two curves. When you move the markers, a triangle is formed between them with the apex at the central anchor (Figure B). Holding down Shift, you can move the guide lines so that there will always be a straight line between the two markers, as shown in Figure C.
An example of a drawing using Bezier curves.