Actions are plain JavaScript objects that describe what happened in the application. They must have a type property and can contain additional data (payload).

// Action object
const addTodo = {
  type: 'ADD_TODO',
  payload: {
    id: 1,
    text: 'Learn Redux'
  }
};

// Action creator function
const addTodoAction = (text) => ({
  type: 'ADD_TODO',
  payload: { id: Date.now(), text }
});