As I know, it's specific for different regions and it means only resulting complectation (i.e. processor i5 or i7, presence/absence of SSD, RAM value -8/12/16, OS type and etc.). In my region, for example, for GL502VM:
GL502VM-FY303 - Intel Core i5 7300HQ 2500 MHz/1920x1080/8Gb RAM/1000Gb HDD+ 128GbSSD/NVIDIA GeForce GTX 1060 3072 Mb/Wi-Fi/Bluetooth/Endless OS)
GL502VM-FY303T - Intel Core i5 7300HQ 2500 MHz/1920x1080/8Gb RAM/1000Gb HDD+128Gb SSD/NVIDIA GeForce GTX 1060 3072 Mb/Wi-Fi/Bluetooth/Win 10); So it has pre-installed OS.
GL502VM-FY243T - Intel Core i7 7700HQ 2800 MHz/1920x1080/8Gb RAM/1000Gb HDD+128Gb SSD/NVIDIA GeForce GTX 1060 6144 Mb/Wi-Fi/Bluetooth/Win 10); So it has more powerful processor and more GPU memory.
GL502VM-FY441T - Intel Core i7 7700HQ 2800 MHz/1920x1080/12Gb RAM/1000Gb HDD+256Gb SSD/NVIDIA GeForce GTX 1060 6144 Mb/Wi-Fi/Bluetooth/Win 10); So it has more RAM and higher SSD capacity.
Do not know if there is any list of them, and you do not need this code anyway, it is easier to choose with specifications listed on shops' page.