ZIP archive of about 2.61 MB for the DEXP C15-I5W302 laptop. The SM prefix most likely stands for service manual, though this is not certain, so look at the contents after unpacking. A service manual typically covers disassembly order, part lists and connector locations, which speeds up teardown and component replacement. DEXP units come from various ODMs, so confirm the exact model and board marking inside the chassis match the documentation before following it.
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 @Boardviewno. Enginerys does not host this file.
How to open a .zip file
Compressed archive that every operating system opens without extra software.
Built-in OS tools7-Zip