Gnome-o-Phone, or gphone for short, is an Internet telephone.
In other words, if you and your friends have computers with sound cards and network connections, you can use gphone to talk to each other and save money on phone bills.
Gphone is definitely a work in progress, and you probably shouldn't bet your business on it. If it breaks, you can keep both pieces.
Don't be too hard on the program, though. Although the user interface is a bit rough, gphone does actually work pretty well.