The term 'kind of curve' can refer to a variety of different shapes. A SINE is a smooth, periodic waveform that is often used in mathematics and physics. A PARABOLA is a symmetrical, U-shaped curve that is the result of a quadratic equation. A bell curve is a symmetrical, bell-shaped curve that is used to represent normal distributions. A HAIRPIN is an S-shaped curve that resembles a HAIRPIN. Finally, an ESS is an elliptical spiral shape that is used in engineering and architecture.