The shooting line, also called the running line, refers to the thin and smooth section of the fly line that sits between the shooting head (Spey, Skagit, Scandi, etc.) and the reel. When using a modern Spey line for salmon fishing, it is often composed of two main sections:
The shooting head: the short, heavy section that loads the rod and propels the fly.
The shooting line: the thin, lightweight, and floating or intermediate section that follows the head and enables long-distance casting.