Schematic for the Lenovo board NM-A221, packed as a ZIP holding a PDF. NM-prefixed numbers belong to LCFC, the Lenovo-owned ODM that designs many ThinkPad and IdeaPad boards. The schematic lets a technician follow power rails from the charger input through the system regulators, check signal paths between the chipset and peripherals, and find which components sit on a shorted line. It opens in any PDF viewer; check that the board number printed on the PCB matches NM-A221 before trusting the pin and net names.
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 @schematicslaptop. Enginerys does not host this file.
How to open a .zip file
Compressed archive that every operating system opens without extra software.