With manual drafting tools, you can draw a point curve (a curve through a series of points) with a French curve. Promis.e has, in effect, a variety of mathematical French curves for placing curves on the basis of data points in the design plane, including point curves and NURBS (non-uniform rational B-splines).
Composite curves actually can consist of a combination of line segments, arcs, and Bézier curves.
You can draw curves without any understanding of the mathematics behind them, or you can create curves based on sophisticated mathematical formulas.
The easiest way to become familiar with curve placement tools is to enter a series of data points or a line string, then construct different curves based on those elements. With B-splines, you can adjust the settings as you watch the curve update, then accept the curve when it has the correct shape.