If you own property with another person as joint tenants with right of survivorship, that is, not as tenants in common, the property will pass directly to the remaining joint tenant upon your death and will not be a part of your probate estate. (It will, however, be a part of your taxable estate.) Frequently, people (particularly in old age) will cause bank accounts or securities to be placed in the name of the owner with one or more children or trusted friends as joint tenants with right of survivorship. This is sometimes done as a matter of convenience to give the joint tenant continuing access to accounts to pay bills.
It is important to realize that the ownership of property in this fashion often leads to unexpected or unwanted results. Disputes, including litigation, are common between the estate of the original owner and the surviving joint tenant as to whether the survivors name was added as a matter of convenience and/or management or whether a gift was intended. The planning built into a well-drawn will may be partially or completely thwarted by an inadvertently created joint tenancy that passes property to a beneficiary by operation of law, rather than under the terms of the will.
Many of these problems are also applicable to institutional revocable trusts and "pay on death" forms of ownership of bank, broker, and mutual fund accounts and savings bonds. Effective planning requires knowledge of the consequences of each property interest and technique.