Zipped schematic package for the phone model G570F, with the .M suffix usually marking a mainboard set in this naming style; the code follows Samsung's SM-G570F pattern, but nothing else about revision is stated. Inside you can expect diagram pages, typically PDF, covering power management, charging, RF and connector circuits. Technicians use it to follow a dead rail back to its source, identify filter capacitors and fuses, and find test points. Extract the archive first and check the PCB markings match before working from it.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @phoneSchematics. Enginerys does not host this file.
How to open a .zip file
Compressed archive that every operating system opens without extra software.