Schematic archive named only M33, with no brand given, a 940 KB ZIP. The name is too brief to identify the device reliably; it may be a phone model code, but that is not confirmed. Unpack it and check the title block on the sheets to see which product and board revision it covers. Once matched, schematics like this are used to trace power rails, find test points, and check signal paths during fault-finding.
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.
Built-in OS tools7-Zip