What is an IMEI number? How to find yours?

Moreover, Dual SIM devices have a separate IMEI code for each card slot, in order to differentiate the two connections This code is permanently associated

Serial number : The following six digits denote a unique serial number defined by the device manufacturer IMEI 2: Assigned to the secondary SIM slot

imei sv slot 1 Serial number : The following six digits denote a unique serial number defined by the device manufacturer IMEI 2: Assigned to the secondary SIM slot

imei slot my phone has two IMEI numbers, when transferring numbers does public mobile need the IMEI of my used SIM slot or the avaliable SIM slot?