What is the necessity of both p-n-p and n-p-n transistors?
The circuit diagram below is, a circuit for making simple solar powered toys. I picked this as an example because it includes one of each, 1 PNP, 1 NPN, both wired in the manner that I claim these things are usually wired.
For the PNP: Ic+Ib flows into the emitter, then they split: Ib flows out the base and Ic flows out the collector.
For the NPN: Ib flows into the base. Ic flows into the collector. Then Ib and Ic sort of merge together and Ib+Ic flows out the emitter.