If you ever buy a property through a mortgage and realtor, then you have seen the commitment of the title. The title insurance company alerts you to who owns the property you buy and liens, mortgages or encumbrances on the property.
It is important that you get the title and title insurance commitment. A typical sales agreement requires the seller to give the buyer a "warranty" deed. You can talk to national title insurance underwriters to get all the information regarding title insurance.
The word "guarantee" means that the seller guarantees the buyer that he/she owns the property, which consists of a description of the set of laws contained in the commitment of the title, and that liens, encumbrances, and mortgages will have been exhausted at the time of closing so that the property is transferred without any difficulty.
As an aside, if the sales agreement is signed by one person but the commitment of the title indicates that there are two property owners; both owners must sign the closing documents for the sale to be realized.
If the property is owned by a real (because the owner died), the personal representative may need to obtain a court order to obtain the authority to sign the deed on behalf of the estate.
If the property is owned by a company, then the majority of shareholders must approve the sale through the resolution of the company for the sale to be effective.