Bogoliubov transformation (in Russian literature, it means the love of God transformation) is a quantum mechanical transformation to define an approximate vacuum state, a nearly zero energy state, (also called ground state), to explain the violence of conservation of fermion and antifermion number in an interaction. If you know the Bogoliubov angles, you can operate the creation operator on the vacuum state to construct boson state. Thus, this transformation is a unitary transformation, you can say from vacuum to boson state transformation .
If a pair of coupled harmonic oscillators are described by coordinates( x1,p1,x2,p2) and a canonical transformation is introduced to decouple them, then the set of transformation matrices behave as if it is a Lorentz transformation in 2+1 dimensions. This is Bogoliubov transformation. For a detailed discussion in the context of Condensed Matter Physics, see