A huge amount of internet traffic (over 80% according to Google) is API calls. Modern webapplications also often make use of APIs not just for calls to third party applications but for core functionality and communication between the client and server.
It’s critical that we understand how to effectively enumerate and test APIs.
I have published a course called Practical API Hacking that can be found on the TCM Academy. If you‘re curious about it feel free to check it out or drop a message on the TCM Discord if you want more info about it.