I recently change to mac and I'm lost

http://www.apple.com/support/macbasics/

Isolating Issues in Mac OS

http://support.apple.com/kb/TS1388

https://www.apple.com/support/osx/

https://www.apple.com/support/quickassist/

http://www.apple.com/support/mac101/help/

http://www.apple.com/support/mac101/tour/

Get Help with your Product

http://docs.info.apple.com/article.html?artnum=304725

Apple Mac App Store

https://discussions.apple.com/community/mac_app_store/using_mac_apple_store

How to Buy Mac OS X Mountain Lion/Lion

http://www.apple.com/osx/how-to-upgrade/

TimeMachine 101

https://support.apple.com/kb/HT1427

http://www.apple.com/support/timemachine

Mac OS X & Mountain Lion Community

https://discussions.apple.com/community/mac_os

https://discussions.apple.com/community/mac_os/os_x_mountain_lion?view=discussio ns

Recovery Mode

http://support.apple.com/kb/HT4718

ExpressLane

https://expresslane.apple.com/

Startup Manager: How to select a startup volume

http://support.apple.com/kb/HT131

Startup Key combination: here is the old list:

http://support.apple.com/kb/HT1343

And also:

Switching from Windows to Mac:

http://support.apple.com/kb/HT2514?viewlocale=en_US

and

http://support.apple.com/kb/HT2518?viewlocale=en_US