Appears to be a type of softphone.
Because Nolia PC Phone only works with Nokia handsets, it appears that the goal of this new offering is to offer a desktop version of Nokia phones. In other words, Nokia cell users who are at home can use their mobile phone connection while being on the Web at the same time.
Since I don't have a Nokia phone, I haven't tried out this solution yet. I would be interested in hearing from some of you that have.