MRO stands for maintenance, repair, operations. Any item used in these processes is termed an MRO good or item. These are the goods that are not part of the end product, are not central to the company's output, yet are mandatorily utilized. One can think of a large number of MRO goods. In the maintenance of factory space and equipment, cleaning supplies are used. A lot of office supplies are required for business, yet are not part of the final product. The same is true of office furniture, computers, and communication devices. One can also think of pumps, compressors, oil, grease, etc. used for the repair and daily maintenance of equipment. Any supplies required to repair and operate any mechanical, electrical or plumbing works are also part of MRO goods.
Hope this helps.