To see a list of all events use this command
php bin/console debug:event-dispatcher
Built-in Symfony Events – this covers some of how events work in Symfony and the basic default events that fire with every request.
The HTTP kernel component – This gets to the core of Symfony and it’s event system. The kernel is driven by events. This also covers the basic flow of events that symfony follows when a request enters the system.
Events and event listeners – More information about symfony events.
The EventDispacher component – This is more about the symfony system events.
An example of how to use the EventDispacher component
This video covers how to create a custom event subscriber