Pre-booking specifically denotes that you have booked something in advance,

Book (something) in advance: a pre-booked hotel reservation (ODO)

whilst booking

Reserve accommodation for (someone): his secretary had booked him into the hotel (ODO)

merely connotes these meanings and booking would refer to the reservation more generally and motto the act of booking it beforehand

Pre-booking specifically denotes that you have booked something in advance,

Book (something) in advance: a pre-booked hotel reservation (ODO)

whilst booking

Reserve accommodation for (someone): his secretary had booked him into the hotel (ODO)

merely connotes these meanings and booking would refer to the reservation more generally and not specifically the act of booking it beforehand

Pre-booking specifically denotes that you have booked something in advance,

Book (something) in advance: a pre-booked hotel reservation

whilst booking

Reserve accommodation for (someone): his secretary had booked him into the hotel

merely connotes these meanings and booking would refer to the reservation more generally and motto the act of booking it beforehand

Pre-booking specifically denotes that you have booked something in advance,

Book (something) in advance: a pre-booked hotel reservation (ODO)

whilst booking

Reserve accommodation for (someone): his secretary had booked him into the hotel (ODO)

merely connotes these meanings and booking would refer to the reservation more generally and motto the act of booking it beforehand