Lenovo E255 schematic delivered as a 928 KB PDF. Apart from the model, the name gives no motherboard number, manufacturer or revision, so check the first page of the document for the project code. Technicians use a schematic like this to follow power rails, understand the startup sequence, find which components feed a shorted line and confirm part values. Any PDF reader opens it and text search finds net names quickly. Match the board marking before relying on rail names or component references.
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 @alischematics. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.