Shifting and Fronting are completely different.
Shifting is something some kin experience.
Fronting is something that all multiple systems experience.
Shifting is when any person takes on a transformation of some kind. It was originally short for shape shifting.
In kin terminology Shifting mean they are transformed in some way more fully into one of their kintypes/kinselves. They are feeling a strong mental or astral connection to that kinself. They may be feeling phantom/astral limbs, perceived difference in body type, voice, etc. The person who has shifted is the same person, only temporarily transformed in some way, rather like a werewolf.(for example).
Not all kin experience shifts.
Fronting is when one distinct and separate member of a system takes over the body functions of the shared body.
Each member of a multiple system is a distinct and separate entity. No transformation occurs, rather two members merely switch places, and change who is controlling the body. When Tom is fronting he is completely seperate from Suzie
Imagine a car.
When someone is fronting, the car stops, and one of the passengers moves into the drivers seat and changes the station on the radio.
When someone is shifting, the driver grows the head of a wolf, and sticks his tongue out the window, leaving his favorite station playing on the radio.