API stands for Application Programming Interface. As the name already suggests, it is an interface used to link your ProfitBird with exchanges where your funds are located.
If you provide your ProfitBird account with the API Key and Private Key of your exchange account, then your ProfitBird is able to invest and trade on your exchange account on your behalf. So the API Key and Private Key act as a unique identifier for authentication.
Note that you can assign access rights to your API Key and Private Key if you generate them. We always recommend to disable the permission to deposit or withdraw funds from your exchange account using the API Key and Private Key. This means that ProfitBird does not have access to your funds.