Beta Guess

Key Beta Guess in SABR Model refers to the initial guess value of the SABR parameter β in the SDE for the forward F: dF = αₜFᵝdw
β affects the skew of the implied vol.
Setting it to 1 corresponds to the log-normal model with a flat vol, i.e. no skew.
Setting it to 0 corresponds to the normal model with a very pronounced skew.