You may want to start by looking at Apple's web pages about the MacBook Air and the MacBook Pro. You will also want to check out the Apple store online for the prices and configurations available - Air & Pro.
Another place you may want to look is Apple's support site, including this article about switching from Windows to the Mac OS.
Beyond that, as shldr2thewheel says, if we are to advise you we will need to know more about what you plan to do with the computer and what your portability needs are.
Best of luck.