The primary difference with Apple Macs is that they are made to run Apple's own operating system called OSX and not Windows.
The advantages of that are that the hardware and software are customised for each other which means they tend to work much better together - fewer crashes, optimised performance etc. Another advantage of OSX is that there are few (if any) viruses which target it.
Apple's computers also come with built in software for managing your digital photos, editing movies, recording musical instruments, encoding DVD's and basic web authoring.
I found OSX extremely intuitive to use and it didnt take me very long at all to adjust to using it.
The computers parts however are the same that you would find in other PC's. This means that you can now run Windows on a Mac if there is particular software you need that doesnt have an OSX version.
There is a version of Microsoft Office for Mac which will be fine for many users needs. Power users dont like it as Excel for Mac doesnt support Visual Basic. If you need to use a version of Excel that supports Macros then you will need to run the Windows version.
There are an increasing number of games being released for OSX. Blizzard (maker of World of Warcraft and others) release all their games for Windows and OSX simultaneously. Unfortunately many others developers dont and you sometime have to wait for months for and OSX port of games. Of course if you are an avid gamer you can always run the games on Windows and have the best looking laptop around.
Apple has quite a lot of support for switchers on their website. Check out
http://www.apple.com/support/switch101/ and also
http://www.apple.com/getamac/
Hope this has helped!