Do employees need special training to use the computers?
Yes, a modern retail information system requires special training before the employees can use it for daily transactions. It is provided by the employer or an IT vendor.
Are servers kept in the back of the store?
Most servers are kept at remote locations for safe keeping. Unless there is only one store, then the server will be in the back.
Is there a computer somewhere else linked to computers in the store?
Computers in the store called clients are linked to a computer called server in a central location.
Do they ever break down? What happens if they do break down?
Computer breaks down all the time. That is why company has an IT department or an IT vendor to maintain and repair them.