Datasheet in PDF, about 91 KB, for the 93C66 serial EEPROM, the 4 Kbit member of the widely used 93-series Microwire family; the _3 suffix in the name likely marks a document revision or a low-voltage variant and is not explained further. These memories store settings and identification data in many appliances and boards. The sheet gives pinout, ORG pin function for 8-bit or 16-bit words and timing, which you need when setting up a programmer to back up or restore the chip contents.
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 @cyberlanelectonik. 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.