In short
ERP is enterprise software that manages business processes such as finance, purchasing, sales, inventory and human resources in a single integrated database.
The core value of ERP is that departments look at the same master data and the same transactions. A sales order flows through to inventory, production, shipping and accounting records.
ERP systems usually offer broad but shallow coverage. For detailed shop-floor planning, quality, maintenance and traceability they commonly integrate with specialised systems such as MRP, MES, QMS or CMMS.