PDF datasheet identified by the part code LM315STA-SSA1, a 1.91 MB document. The file name gives only the part number, so the exact component category is not stated beyond the code itself. Datasheets like this are consulted for pinout, electrical ratings, mechanical dimensions and recommended operating conditions when sourcing a replacement or checking whether a substitute part is compatible. Compare the full marking and suffix on the physical component with the code here before using the specifications.
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 @cdispdata. 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.