The largest copy of the UG-2828GCEAF02 display module datasheet here, a 3.23 MB PDF, which may include extra drawings, application circuits or higher-resolution figures than the smaller versions. Typical content includes pinout, electrical ratings, power sequencing and interface timing. Technicians use it to probe supply rails, verify the reset and data lines and wire a replacement module. Check revision notes against the other copies in the set to make sure the values you rely on are current.
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 @acodis_lcd_datasheets_EDID. 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.