What does John 18:24 mean?

Earlier in this same passage, the person questioning Jesus was referred to as "the high priest" (John 18:19). That man is Annas (John 18:13). Secular history tells us Annas was the high priest until around AD 18, when the Romans replaced him with his son-in-law, Caiaphas. Old Testament law made the high priesthood a lifetime appointment (Numbers 35:25), but the Roman Empire preferred to be more in control of their conquered territories. It's possible Annas was considered the "real" high priest by the Jewish people, yet Caiaphas held that title according to the Romans. So, what happens here is Jesus being taken from the [legitimate] high priest to the [government-approved] high priest.

As noted earlier (John 18:14), it was Caiaphas who advocated that Jesus be killed, innocent or not, to prevent His ministry from creating further harm (John 11:47–50). This sequence of sham trials is only for show: the religious leaders of Israel have already made up their minds to put Jesus to death (Mark 14:1–2).