Master data
Items, customers, suppliers and workers — attribute groups, effective dating, and the two traps of organizational scope.
Master data is the records everything else points at: items, customers, suppliers, workers, accounts, patients, students. It sits under its own layer, with attribute groups that let a record carry far more than one form could sensibly show.
Attribute groups
An item is not one flat row. It has purchasing attributes, sales attributes, planning attributes, costing attributes, quality attributes — each a group, each edited on the item rather than on a screen of its own. The cross-item list of one group still exists by address and from a saved view, which is how you compare a planning parameter across two hundred items.
Effective dating
Master data that changes over time is versioned rather than overwritten. A price, a rate or a grade has a window, and asking for it as at a date returns what was in force on that date. See What may be changed for how an edit chooses between correcting the version in force and opening a successor.
Two things to watch with organizational scope: a master record with no unit is visible from every unit, which is sometimes what you want for a shared catalogue and is usually an oversight; and a record created while a narrow unit is selected inherits it, so a catalogue item created from inside one department may be invisible to the next.