What is app in ari/events?app=, do I have to create them manually, or asterisk have them predefined

I was trying to use ari/events but I am not sure what the ‘app’ parameter is in the query_params, do I have to create it manually or I can have some predefined apps?

They aren’t predefined. They are created when a websocket is established to Asterisk, and as part of that websocket you specify the application name.