The airline says "Discover Portugal on the way."  They are inviting travelers headed to Europe to take advantage of special offers that will allow them to visit Lisbon or Porto on their way.  TAP is promoting this as an opportunity to visit two places for the price of one.

With this offer, travelers can spend a night or two, or even more in Lisbon or Porto while on their way to the final destination.  The "stopover" deals includes special hotel rates and even a free bottle of wine at certain restaurants in Lisbon or Porto.

Sounds like a great way to break up a long trip and enjoy what Portugal has to offer.  The TAP offer is available for one-way and multi-city trips.