: This indicates the image size/resolution . The "n" usually stands for "normal" size (standard web resolution). Other variants include _o for original (high res), _s for small/thumbnail, or _b for big.
: This acts as a unique hash or signature generated by the server to ensure the file can be retrieved even if there are multiple versions (like different sizes) of the same image. 67844652_427904021404294_7728310615655055360_n.jpg
: This is often the User or Page ID . It identifies the account or public page that originally posted the content. : This indicates the image size/resolution
: While difficult for modern private accounts, these numbers were historically used to reconstruct direct links to the Facebook profile or the public post they came from. _s for small/thumbnail