Hello sunny_guyed,
A Bridging Open Work Permit (BOWP) is the permit given to you after the expiration of ur PGWP. As you know, your PGWP cannot be extended once it expires. Instead, during the validity of your PGWP, you are expected to apply for your PR.
Different provinces have different requirements before they give you a nomination. Some require that you would have worked for a year in a profession related to your course of study, some require you work for just six months whether in an area related to your course of study or not. Once you have been nominated by the province, you should send your package to CIC and receive your AOR.
You can apply for the BOWP when your PGWP remains one month to expire and you have received your AOR. I am not sure of the validity of the BOWP.
I hope this information has been helpful.
Cheerz