They are used if you want to get BO data from a third-party program. You will call the BO web services and the API key will need to be included to identify you (like retrieving orders, etc). If you are using bricksync, you will need to setup the API Key to allow access to your account.
You can download free programs like Postman as an example, then call the raw data from the BO server for say your orders, your inventory, etc. I'm unfamiliar with APIs, but was able to stumble my way through it - and really learned over time that I didn't really need it for how I do business, the straight download options in our stores work fine for my needs. :-) It is wildly useful for advanced sellers that are computer or programming savvy, that are autoimporting data into offline tools, I suspect. :-)
Comments
If you are using bricksync, you will need to setup the API Key to allow access to your account.