Being 'in parity' with OTAs means that your direct price is equal to the price that the OTAs are offering. If you can display the fact that you are in parity with the OTAs on your own website, then guests can clearly see that there is no added value to booking through an OTA. 

Being 'cheaper direct' means that you have a lower price on your website than can be found on any OTAs, while being 'undercut' means that there is at least one OTA offering a lower price than are offered on your website.