Turn
A Turn is simply one player's turn to act in Combat.
On a turn you may perform an Action and Movement.
Your ability to perform a Reaction this Round is refreshed at the start of your turn.
When all PCs and NPCs have taken a turn, the Round ends and the next round starts.
Fast Turn
A PC that takes a Fast Turn acts before the hostiles in Initiative.
On a Fast Turn, a PC may only perform one of their Action and Movement, not both.