Hello and Welcome to the Support Community
A flashing folder would indicate one of three things.
1. You trying to boot from a network device that's not available
2. Your iBook does not have a OS installed.
3. Your Hard drive has failed.
If it gets stuck on the Apple Logo, it means that it's trying to load a OS but having some difficulties.
Has this iBook been upgraded recently? New memory, hard drive, OS?
Which iBook do you own?
Do you know what version of Mac OS was installed on this iBook?
Try resetting the PMU and see if that provides you with any solution.
We are going to need further details of what iBook it is to assist you further.