There're two different chips in a Macintosh - one for Intel based Mac computers and another for PowerPC (PPC). Siva's blogged about it in his OS X 10.4.10 - go fetch! post, and also, more download information are available under Apple downloads as well.
Here are 4 easy steps I did to download the new OS X 10.4.10 on the Power Mac G4 I use:
1. Before updating the Mac, go to spotlight in a mac and search out your Disk Utility.
2. Next just proceed to repair disk permissions and wait till it's done.
3. Then carry on to update your Mac.
4. After it's done, Siva recommends to repeat the "repair disk permissions" step again.
Repairing Disk Permissions
This only gets the Combo pack onto the G4. It has to be manually installed. And that will be for another post to come.