What you think, what you say, and what you do should all match.
If you hate broccoli but say you love it, that's ~INTEGRITY.
If you promise to mow the lawn, but don't plan to mow the lawn, chances are you won't do it ~INTEGRITY.
Integrity is preserved if you mean what you say and keep your promises. Integrity is lost if you pretend to support a point of view but either don't care or are secretly opposed. Integrity is forfeit if what you do and what you believe are related only to the degree you get paid.