Clarification on Boost function in ROOT


I am recently using the Boost vector in ROOT and wanted to understand the following line:

" A boost in a general direction can be parameterised with three parameters which can be taken as the components of a three vector b = (bx,by,bz). With x = (x,y,z) and gamma = 1/Sqrt(1-beta*beta) (beta being the module of vector b), an arbitrary active Lorentz boost transformation (from the rod frame to the original frame)"

Could you please clarify if in the above statement the rod frame refers to the rest frame of the particle?

Thanks & Regards,

@moneta can you help ?


for the correct definition of the Boost function