What is it particularly useful for e.g. undergrowth, and why is it so cheap compared to the carden scythe for example? Thank you

The main difference between a scythe and a sickle is that a scythe has a long curved blade with a long handle while a sickle has a short handle and a short blade. The cutting width of a scythe is also much greater than that of a sickle. The sickle can be swung in both directions either away from the user, or holding the plant in one hand and the sickle in the other, swinging the sickle towards the user. A sickle is best suited to controlling undergrowth and weeds while allowing you to protect young trees and shurbs.