The card can be reloaded with money. The card gives the recipient gold level membership in the Starbucks rewards program. This includes a free birthday drink, and a free drink or food item after the purchase of 12 drinks. Paying with your registered Starbucks Card gets the cardholder brewed and iced coffee and tea refills at no charge during your visit at a participating store.
It's not a bad deal for someone who goes there every day.