Which manufacture? I'm a Toyota guy, so: https://toyota-usa.epc-data.com/ for parts. I know BMW has something similar, I'm sure the rest do too. These are often called parts manuals, parts fiche, parts catalogs.... you can sometimes find them online (my link), but more often you'll have to hunt them down on torrent sites or the like. Don't expect to find them for vehicles within the past few years. There are also service manuals, and those walk you through the process but rarely have good photos. Still essential to working on a vehicle. I like both digital and hard copies. I have laminated pages for Common service items that I keep with vehicle specific specialty tools, usually for torque specs and fluid types/volumes.