Keyboard Shortcuts/Modifier Keys I am new to Mac (from Linux/Windows background), I find the modifier keys very confusing. I have tried different combinations of modifier key settings but didnt get it to work as expected.

Managed to get Ctrl+C/P to copy/paste but how do I do Alt+Tab to switch Windows.

Also, I like how I can press the Windows button to enter the dashboard/launcher in GNOME 3. How might I do the same in Mac?
Generally the keyboard shortcuts you are used to will rely on the command key.
One nice thing about a lot of Mac OS X menus is they will list the shortcut next to the command in question, and you can type the name of the command in the help menu when using the application in question, hover or use the arrow keys to select the menu item options that appear, and see the keyboard shortcuts.

CMD Tab is application switching, CMD C is copy, CMD V is paste, CMD Space is spotlight, swipe up with four fingers is the launcher iirc.

Also if you are in the Finder, you can click help and type shortcuts, there are lists upon lists for various tasks.