The MX - Mathematica Serialized Package File is a binary package desktop application that is used in computing and visualizations. The MX - Mathematica Serialized Package File was designed and developed by Mathematica and is capable of storing Mathematica expressions in a (proprietary) serialized format that has been optimized for the sake of fast loading. This file is used in the process of distributing certain Mathematica packages. These packages by Mathematica are created by using the DumpSave program and the file can be read using GET.
You can import the MX - Mathematica Serialized Package File by simply using the import command and by using the export command, the file can be exported. Being that MX files are saved in binary format they are not human readable. Another noteworthy observation is that this file cannot be shared between multiple versions of Mathematica or Mathematica versions installed on different types of operating systems.