Page 53 - Beginner's Guide to Aviation

For transfer, the bags are mixed with other arrival bags in the trolleys or containers. They are separated at the offloading area, where they will then join departure bags. Early bags are stored at special facilities until it is time to dispatch them to the departing aircraft.
FUN FACT:
The baggage tag includes information such as: airline name, flight number, destination or transfer airport name, a 10-digit bar code and others (e.g. passenger’s name). The tag helps in passenger and baggage reconciliation, which is the process of confirming whether the owner of the bag has already boarded the plane.
Thirdly, the passenger loading bridge (PLB), also known as the aerobridge, is used to allow passengers to board and disembark the airplane without having to go outside. It extends from the terminal building to the aircraft.
There are two types of aerobridges, the pedestal and the apron drive. The main difference between these two aerobridges is, pedestal can serve limited types of aircraft only, while apron drive can serve all aircraft types. This is because pedestal PLB has a fixed door height which cannot be readjusted to match other aircraft door heights.
PLB
aircraft