A multiarch environment allows the execution of binary executables for
multiple architectures: The host architecture, and any other architecture that support is added for. Multiarch environments can be used for cross-platform development and
(limited) testing of user-space programs for a foreign architecture.
This can be very helpful in case access to IBM Z or LinuxONE hardware is limited: By utilizing multiarch environments, developers can conveniently develop code e.g. on their laptops in an environment of their choice.
See full instructions on how to set up a multiarch environment for s390x here.