They are both preamplifiers. Linestage is the term used to describe a preamp without a phono section for the TT/cartridge. So the linestage only accepts line-level components such as CDP, tuner, streamer.
A phonostage (phono preamp) is a dedicated device that accepts the low-level gain of a TT/cartridge and then plugs into a linestage. Some preamps will have a built-in phonostage.
A phonostage (phono preamp) is a dedicated device that accepts the low-level gain of a TT/cartridge and then plugs into a linestage. Some preamps will have a built-in phonostage.