Have you ever played with toy trains and tried to connect them together? They probably had a little hook on the front and back that you had to snap together to make them stick. When real trains connect to each other, they have something similar called a coupling.
Sometimes, trains from different places have different types of couplings. Think of it like trying to play with a toy train that has a different hook than your other trains - they just won't stick together! When that happens with real trains, they can't connect and travel together.
To be able to connect trains together and travel far distances, they need to have the same type of coupling. This is where railway coupling conversion comes in - it's the process of changing the coupling on one train to make it match the others.
It's kind of like changing the toy train's hook to match the other trains you have. But instead of just switching out a piece, it's a big job that needs special tools and people who know how to do it safely.
Once the conversion is done, the different trains can connect and travel to new places together, just like your toys would when they all have the same type of hook. And that's how railway coupling conversion works!