Where are pigtails and fiber optic patch cords used respectively?

Weak power project, pigtail and fiber optic patch cords are used in where? First of all, let's figure out what is a fiber optic patch cord, what is a pigtail, what is the difference between them, like this has two fiber optic connectors called patch cords, you can connect the two devices, such as fiber optic transceivers and terminal boxes are connected through the fiber optic patch cord. Like this only one end with a connector, the other end is a fiber optic cable core breakout is pigtail, usually used in fiber optic terminal boxes, fiber optic distribution frames, fiber optic panels, etc., and then through the fusion splicing and other equipment connected.