What is the item or the records?
In each datasheet you keep records that belong to it, for which it is intended. For example in the Companies you have a list of individual companies, in the Employee register you have a list of all employees. Individual companies or employees are then records (items) in the datasheet. You can also imagine them as rows in Excel, or individual sheets in a file cabinet.
The datasheets therefore consist of a list of records (items).