Process submit notification

Hello,
I don't know if you understand me very well, I'm French and I'm not very good in English, so sorry for mistake.

I develop a plugin which reply like I need. I have succeed to create my form so that users can subscribe. My issue is the following :
I don't know what are the functions called when an event is achieve. How can I check if the event match with my params and so say to send an notification?

Please, answer me or ask me more info if necessary.
Thank you for all who will answer