Amazon Store Card vs Credit Card: What's the difference?

The main difference between the Amazon Store Card and the Amazon Credit Card is that the former can only be used to make purchases at Amazon and where Amazon Pay is accepted, whereas the latter can be used pretty much anywhere in the world.
This leads to a second difference, which is the approval requirements. It's easier to get approved for the Amazon Store Card, which requires just fair credit and even limited credit history, while you'll need at least good credit to get the Amazon Credit Card.
The Amazon Credit Card also offers better rewards and a better initial bonus if you have Amazon Prime ($70 gift card vs. $10 gift card), plus it rewards you for non-Amazon purchases as well with 2 points for every eligible $1 spent at gas stations, restaurants and drugstores, and 1 point for every other $1 spent.