ZIP archive, 2.18 MB, labelled for the Huawei Y300 phone with no document type given in the name. Expect service material such as a schematic or board layout inside, but open it to confirm. It is meant for board-level work: following supply rails out of the power management chip, identifying parts and their values, reading flex connector pinouts and finding test points. Note that the Y300C is a separate variant; confirm your device is the plain Y300 before relying on the details.
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 @cyberlanelectonik. Enginerys does not host this file.
How to open a .zip file
Compressed archive that every operating system opens without extra software.