While it is easy to say that probate property is only the property that passes under the terms of your Will, that definition doesn’t help much. The best way to understand what is probate property is to realize it is what’s left over after all of the non-probate property has passed.
Non-probate property passes to someone upon the owner’s death, either by operation of law or as a result of contract rights. Follow the links to see examples of this type of property. There is also more information regarding avoiding probate with respect to securities (stocks and bonds), bank accounts, real estate, retirement plan assets, and motor vehicles elsewhere on this site.
Remember, however, whether or not property is probate property has little or no bearing as to whether the property is subject to estate tax.