It used to be that this kind of information wasn't readily available and that unless you knew a bunch of pilots and they were very forthcoming, you really couldn't get this information much ahead of time. Times have changed with the internet and these topics are covered in many places on this site. I suggest starting to do searches and scouring these forums, start working backwards and do some research. You'll quickly start to understand. Like most industries, you aren't going to get hired at the upper levels without significant experience. There are multiple ways to build that experience, some involving "airlines", but airlines are everything from single-engine piston airplanes up to A-380s. Learn about the industry and the different 14 CFR parts that certificate holders operate under, that will start to help you as well. Do all of this before diving head-first into pilot training to gain an understanding. Far to many of us did our training without much of an understanding of the industry due to the limitations on information many years ago.