“My photo collection is scattered across three or four different computers.”
You're telling your friend about an amazing trip you went on seven years ago. He asks if you have pictures, but you explain that you're not sure exactly where they are.
My photo collection is scattered across three or four different computers.
A "photo collection" is a bunch of photos that a person has. Your photo collection might be physically printed photos, or digital photos stored on a computer or in the cloud.
She had the most amazing photo collection!
When things are "scattered", it means that they are located randomly around a location. They're not straight, grouped together, or in order. Imagine a stack of cards which have been dropped on the floor:
The cards were scattered all over the floor.
When things are "scattered" in several different locations, you can use the phrase "scattered across ___". For example:
These days, my family is scattered across a dozen different countries around the world.
Different pieces of information are scattered across different departments, and it's hard to figure out who knows what.