Imagine you and your friends are playing tag in a big field. But there are some parts of the field you can't go into, because they're too dangerous or messy. So, your grown-up sets up a fence around those parts of the field.
The fence is there to keep you safe, and to make sure you don't accidentally run through a dangerous or messy area. But it also lets you keep playing your game of tag, because you can still run around the parts of the field where it's safe.
In computer science, a "via fence" works the same way. It's a way of protecting parts of a computer's memory so that certain programs or processes can't accidentally mess them up. When you have multiple programs running on a computer, it's important to make sure they don't accidentally overwrite each other's data.
So, a via fence creates a boundary around certain parts of the computer's memory, so that only certain programs can access them. This keeps everything organized and safe, just like the fence in the field.
Overall, a via fence is a way of keeping different parts of a computer's memory separate and protecting them from damage or corruption.