Apple's Wallet is where you can store all of your debit and credit cards on your iPhone, as well as concert tickets, boarding passes, loyalty cards, and more. If you didn't receive a link from a particular company in order to automatically create a pass, what can you do?
PassSource is the key to creating Apple Wallet passes that you can use on your iPhone and Apple Watch. If you're a business owner, you can use PassSource's templates to create your own official passes.
If you're not a business owner but still want to create your own passes, you can totally do so. You can also include push notifications, location alerts, and more.
Creating passes takes a bit of knowhow and may even take a bit of coding on your part, though PassSource provides many free templates for you to use. If you pay a subscription fee, you can also gain access to some premium features, like the ability to use the API and customize things further.
If you're just looking for which companies have official Apple Wallet passes, then PassSource has a full list. The list isn't complete, and some of the links are outdated, but if you know of a company that has its own official Apple Wallet pass, you can let PassSource know and they'll add it to the list!