PDF titled BQ738, which matches the naming of Texas Instruments bq738xx battery charge controllers common on laptop boards. The name does not state the exact suffix, so check the document against the chip marking. At 1.88 MB it is likely a datasheet describing pinout, typical charger circuit and adapter detection behaviour. Technicians use it to test charger inputs, ACDET and gate drive when a board will not charge or run on adapter.
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 @opendatasheet. 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.
Any PDF readerSumatraPDFFirefox / ChromeFlexBV (links PDF to boardview)