Ive just started playing golf with my grandads set of clubs (i havn't played since i was about 12, 9 years ago) and obviously the clubs seem to have changed a fair bit, i was reading about hybrid clubs earier which seemed pretty interesting but then i got round to looking at putters.
Basically the putter i have looks like one you would get if you were going down to a crazy golf course. All the new ones seem to look like this: http://www.americangolf.co.uk/golf-clubs/golf-putters/odyssey-white-steel-2-ball-blade-putter/
What purpose does the huge bit at the back serve?
Are the two white circles of use for anything?