I have found an awesome series of Free Pascal tutorials using Lazarus, on YouTube. The series starts with the basics, what a free pascal actually is. Here it is:
Lazarus is an IDE for Free Pascal, that is, it is a working environment. Once you get hold on Lazarus on one platform, you can use it on other platforms just as well. The motto of Lazarus is Write Once, Compile Anywhere! and it actually holds on to that promise!