A material master gives a reusable identity to an item. Its key stays the same when a description changes. The base unit of measure defines what a quantity means: EA counts individual pieces, while KG measures weight. Confusing the two changes the physical meaning of a receipt even if the number looks reasonable.
The simulator stores the material description, material type, base unit, plant, storage location and valuation price. Create only the data the task requests. These exercises use raw-material type ROH and fictional parts for a small manufacturer. Use MM02 when you update a record, and keep the key and any unchanged fields intact. A supplier's description isn't a substitute for your own material identifier.