MVS or Multiple Virtual Storage is an operating system used for IBM mainframe computers. There are several synonyms for MVS, which includes z/OS, OS/390, and OS/360. Z/OS is the latest version of MVS that includes advanced features like 64-bit computing, enhanced security, and improved storage management. OS/390 and OS/360 were the earlier versions of MVS with limited abilities. Besides these synonyms, there are other operating systems used for mainframe computers, such as VSE and VM. However, MVS is a widely used operating system, and its synonyms are commonly used interchangeably.