I take it you're running this for example in SQL*Plus. & indicates a substitution variable so you need to define a value for it prior to using.
Try using something like
define Entertainer_TYPE = 'Something goes in here'
define Event_date = 'And this contains something else'
Based on the names of the variables it looks like you're handling dates using varchar. If that's true, you should change dates to use
date
type