PDF document filed under the Texas Instruments literature number SDLS109, part of the older TTL logic datasheet series. The name contains no part number, so check the opening page of the 451 KB file to see which device it covers. Datasheets like this give the pin functions, truth tables, absolute maximum ratings and switching speeds. A technician uses them to confirm correct operation with a logic probe or oscilloscope and to choose an equivalent device when the original logic chip is hard to find.
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 @datasheet_technar_org. 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.