Описание тега mat-file
MAT-file is a binary file format, that can stores multiple MATLAB variables. It uses the .mat extension.
MAT-file is binary file format, used to store data in multiple variables or structures in MATLAB. These files use the.mat extension, and can be accessed in matlab using the load, save or matfile functions. For more information, see MAT-File Versions in the MATLAB documentation.
MAT-files can be also created and read by other programming languages such as Python etc.
Refer to this PDF document for a description of the internals of the MAT-file format (Level 4 and Level 5).