A gift account is an activation code that anyone can use to enable a pro account. You can buy a gift account for anyone, whether they’re a member or not (although people who don’t have a Flickr account yet will need to make one as part of the activation.) The person you give the gift to will be sent to a special page to enter their code, and hey presto! the pro account is theirs! Further more, Pro users now have Unlimited space on their Flickr, and regular users now have 100mb a month.
Flickr's got some cool Xmas Easter-egg: Try to add the notes:"ho ho ho hat" & "ho ho ho beard" and get this neat result.