Official Google Blog: Google Calendar Sync

sync mean keeping two or more things changing together to remain same.

Google had launched Google calender synchronising software which will keep you outlook calender and Google calender synchronised.

If you make changes in Google calender, the auto change will be made in outlook calender and vice versa.

you get options like
1.Two way sync
In this if you make changes in outlook it will be updated in Google calender also and vice versa
2. One way sync
here you can sync either Google calender to outlook or other way
"How to do it"

1. Download Google calender sync
2.once downloaded a window will pop up, you can see in screen shot.
3. set the minute after which sync takes place you are all done

but for all above to happen you need account in Google calender app .