"Int" is a really important computer instruction that is used in computers with x86 processors. It's short for "interrupt" which means to stop what the computer is doing and pay attention to something urgent.
Think about when you are playing with your toys, if someone calls your name, you will stop and go see what they need. That's what an interrupt does to a computer, it stops what it's doing (playing with its toys) and goes to see what the interrupt needs.
When the computer gets an "int" instruction, it stops everything else it's doing and jumps to a special routine (a set of instructions) that is already programmed into the computer. This special routine is usually very important and deals with important tasks like managing memory, controlling input/output (like reading from a USB drive), or talking to the operating system itself.
Think of it like interrupting someone who's busy coloring to ask them to pass you a crayon, they'll stop coloring and pass you the crayon before going back to their coloring.
So, "int" is a really important way for computer programs to communicate with the underlying computer hardware, and it's a key part of how we get our computers to do a wide variety of useful things.