What are catridge type fuses? Why must T1 be connected to the live wire and T2 connected to the neutral wire?

A cartridge fuse is a single use, cylindrical sealed structure containing a fuse wire inside and two terminals outside. It is compact, provides better insulation, ease of installation, safety and protects the fuse wire from contact with moisture and air. It is generally used in electronic equipment and stabilizers.

See the schematic diagram for fuse installation

The terminals T1 and T2 are used to connect both end of the live wires and not live and neutral wires, so that if large current due to short circuit flows through the live wire via the fuse; it may burn and save the circuit from further damage. Remember two terminals are not used to connect live and neutral wires, in that case it will result in short circuit and burn the fuse wire.