WIPO has produced a collection of frequently asked questions and their corresponding answers about the Patent Cooperation Treaty (PCT). The PDF document is available here. Questions and answers to:
1) I have an invention. How can I protect it in several countries?
2) What is the Patent Cooperation Treaty (PCT)?
3) What is the effect of an international patent application?
4) Who has the right to file an international patent application under the PCT?
5) Where can I file my international patent application?.......
24) What happens to my application in the national phase?
25) What are the advantages of the Patent Cooperation Treaty?
26) Where can I find out more about the PCT?

WIPO Website