What Does a Will Not Do?
A will does not govern the transfer of certain types of assets, called non-probate property, which by operation of law (title) or contract (such as a beneficiary designation) pass to someone other than your estate on your death. For example, real estate and other assets owned with rights of survivorship pass automatically to the surviving owner. Likewise, an IRA or insurance policy payable to a named beneficiary passes to that named beneficiary regardless of your will.
source http://www.americanbar.org/groups/real_property_trust_estate/resources/estate_planning/an_introduction_to_wills.html
