PDF schematic for the Lenovo E255, 928 KB, with no board number, ODM or revision given in the name. Before relying on it, open the title block on the pages to read the board designation and compare it with the code printed on the PCB, since the model name alone does not guarantee the same layout. A circuit diagram of this kind is used to follow power rails, check what each voltage regulator supplies, trace signals between chips and locate the parts responsible for a short or a no-boot condition.
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 @smschematics. 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.