A 340 KB PDF from Texas Instruments, named solely by its SDLS literature code, the document numbering TI uses for classic TTL logic datasheets. Which device it covers is not stated in the name and must be read from the first page. The contents typically include connection diagrams, function tables, recommended operating conditions and switching characteristics that a technician needs when probing logic chips in circuit or picking a pin-compatible replacement. Check that the board chip marking matches the document.
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.