These are Google Analytics cookies.
__Utma cookies:
This cookie is called a “persistent” cookie because it never expires (technically, it expires ... in 2038 ... but for the sake of explanation, let's pretend that it never expires). This cookie keeps track of how many times a visitor visited a cookie site when their first visit was and when their last visit. Google Analytics uses the information in this cookie to calculate things like Days and Visits for a purchase.
__Utmb and __utmc cookies:
Cookies B and C are brothers, working together to calculate how long a visit takes. __utmb takes the timestamp of the exact point in time when the visitor enters the site, and __utmc takes the timestamp of the exact point in time when the visitor leaves the site. __utmb expires at the end of the session. __utmc waits 30 minutes and then expires. You see, __utmc does not know when the user closes his browser or leaves the website, so he waits 30 minutes for another page view, and if it does not, it expires.
__Utmz cookies:
Mr. __utmz keeps track of where the visitor came from, what search engine you used, what link you clicked, what keyword you used and where they were in the world when you accessed the website. It expires in 15 768 000 seconds - or in 6 months. This cookie is how Google Analytics knows to whom and to what source / average / keyword to assign a loan to convert an e-commerce goal or transaction. __utmz also allows you to edit your length with a simple customization of the Google Analytics tracking code.
Cookies __utmv files:
If you use a custom report in Google Analytics and encoded something on your website for any user segmentation, the __utmv cookie is installed on the personal computer so that Google Analytics knows how to classify this visitor, the __utmv cookie is also a permanent, lifetime file cookie
taken from GA article:
http://www.morevisibility.com/analyticsblog/from-__utma-to-__utmz-google-analytics-cookies.html