Do you know what phones are? They are devices we use to talk to our family and friends who are far away. GSM services are like the helpers that make that happen.
You see, there are many different companies that provide phone services, and they all have different ways of doing it. Some use a system called "GSM."
GSM services are like a special language that phones and phone companies use to talk to each other. It helps them know where you are, who you are calling, and how long you have talked for.
When you use GSM services, you have to put a little card inside your phone called a "SIM card." It talks to the GSM network and lets you make calls, send texts, and use the internet.
So, when you use your phone to talk to your grandma, the GSM services help send your voice to her phone. It's like they are holding your hand and helping you talk to her, even if she is very far away.