Manufacturing Execution System (MES) is not a standard term. Organizations sell finished goods, and to manufacture these goods you create a plan, MES is the execution of manufacturing for this plan.
Almost everyone on automation understands similar things and core functionalities when we talk about Supervisory Control and Data Acquisition (SCADA); however, this is not the case for MES. The most common requirements from an MES are Scheduling, Work Order Management, Performance Metrics such as OEE, and tracking downtime. Even on the most common 4 Scheduling is usually dropped because it is mostly handled on the ERP level or you might go with separate scheduling software; for work order management, ERP can generate manufacturing work orders coming from the routings. Recipe Management, Digital Quality Inspection Plans, Statistical Process Control, ISO Compliance, Digital Work Instructions, BOM, Inventory Management, consuming raw material, WIP and creating WIP, finished goods, kitting, etc. can be addressed with MES as well.
Is MaestroHub MES, the short answer for the bucket of capabilities no; however, MaestroHub provides you the critical two components of machine breakdown tracking and performance metric calculation with a dashboard.