Events are generated when the user interacts with the form, such as updating a field’s value or adding a record to a related list. These events are then passed to any (default or custom) handlers that have been defined for that interaction.
This method will return the new value as a result of the event. For example, if the user enters a text in a text field, this method will return a String representation of what the user entered.
This method will return the value that the field had before the event happened. For example, if the user changes a text in a text field, this method will return a String representation of the old text.