Yes, Ethereum has an API mechanism of access to functions and data it possesses. The single standard for Ethereum APIs is the JSON RPC which provides multiple endpoints for retrieving the data from the blockchain. There are a lot of additional libraries based on a variety of programming languages to simplify your access to Ethereum and provide you with wide functionality.
It’s not the most secure tool, as there are facts of stealing API keys and following unpleasant circumstances. You have to use the protected channels of communications when you get your API keys and establish connections with the most attention to detail. Of course, you should use only reliable API providers and not trust any scam services.
In the terms of Ethereum, an API key is a simple secured string that identifies the connection between your application and Ethereum nodes. It’s important for both encrypted access and billing. It works as an identification and access tool. Without an API key, it’s impossible to establish a connection through the API.
First, you have to select the API of a certain type depending on the purposes of your connection. Then follow the documentation instructions for accessing the blockchain API. It may slightly vary depending on the type, but generally, you’ll have to use a certain library matching your project to apply the API key and establish a connection between the blockchain and your application. Voila, you get your blockchain API.