Q: What is the difference between the G3 and G4 Apple ibooks? How can I tell which one is the one I have?
A: Those are just 2 different kinds of processors. If it doesn't say on the case, you can find your specs under the Apple menu > About this mac. The last G3 updates were about 6 years ago and the G4s about 3 years. Current machines all run Intel processors so don't expect future OS upgrades to run on those old processors.