GSM stands for Global System for Mobile Communications. It's a standard for 2G digital cellular networks used by mobile devices such as mobile phones and tablets. A GSM ROM (Read-Only Memory) refers to the firmware or software that runs on a mobile device, dictating its functionality, including connectivity options like GSM.
Some full packages include multiple CSC files (e.g., CSC_OYM , CSC_VOD ). You must select the one matching your region. Flashing the wrong CSC can disable VoLTE or Wi-Fi calling.
That is a "one-file" or "all-in-one" Odin package. Load it into the slot only. Do not use BL, CP, or CSC. Ensure "Auto Reboot" is checked.