Event handlers are functions or routines that handle or respond to specific events in a program. 'Search' is an event handler that can be used to handle search-related actions. 'Form input' is an event handler used to handle user interactions with forms, like input fields. 'Visualization' is an event handler used to handle events related to data visualization. 'Set token' is not typically considered a type of event handler but rather an operation carried out by event handlers to manipulate tokens within the system.