An Application Programming Interface (API) Key is a unique identifier that is used to authenticate a developer or program to an API.
When you create a Twilio Account, Twilio generates an Account SID (String IDentifier) and an Auth Token. These are your Account API credentials. Any time you share these credentials, say with a colleague, you increase the risk of those credentials becoming compromised. Luckily, Twilio also allows you to authenticate using API Keys.
API Keys are the preferred way to authenticate to Twilio's services.
Check out the API Keys Overview page to learn about the types of API Keys that Twilio offers and how to create and delete API Keys
Read the "Make an HTTP Request to Twilio" doc to learn how to authenticate your requests with API Keys.