What is title insurance and why is it necessary?
Title insurance is nothing more than an insurance policy that provides assurance to interested parties that there's good and marketable title to the property being insured. However, this never means that title insurance guarantees perfect title. As with all insurance, there are a number of different types of policies and endorsements. There are also many exceptions to title, which all tie back into information in the preliminary title report. These include specific exceptions listed on the property to be insured, as well as standard exceptions.
One standard exception, for example, is that the insurance will only be provided for exceptions to title that are reflected by the public records. Unless a special endorsement is obtained (which costs more money), there's no obligation on the insurance company to insure against defects in title that would have been apparent from surveying or otherwise physically inspecting the property.
There are also different types of policies. For example, it's customary in most states for a seller to pay for standard coverage for the buyer that insures that the deed from the seller is conveying title that it purports to convey, subject to exceptions in the title report. If a buyer wants additional protection against third party claims such as mechanic's liens, the buyer can purchase an owner's policy. If a loan is involved, a lender's policy can be issued that specifically insures the lender against title defects.