PDF of 1.20 MB whose Portuguese title translates to primary and secondary meshes, most likely a reference on primary and secondary power lines or circuits. No phone model, brand or board number is named, so its scope is unclear until opened. Guides of this kind explain how supply rails branch from the battery and PMIC into secondary lines feeding processor, memory and peripherals, which helps when hunting a short or a missing voltage. Open it in any PDF reader and compare its examples against the schematic for the board you are repairing.
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 @esquemaseletricos. 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.