Electrical file | (E-...) | .pdf  | 
BOM file        | (B-...) | .xlsx | Bill of Materials
Layout file     | (L-...) | .pdf  | 
Design file     | (D-..)  | .zip  | Allegro Design files ... -.DSN and -.BRD
Gerber file     | (G-...) | .zip  | files for PCB production
ReadMe file     | (R-...) | .txt  | this file