Title is a legal term for who holds the ownership rights or some interest in a piece of property. When you buy a home, the buyer will perform a title search to ensure that the seller owns the property free and clear, i.e., there are no liens (or claims) against it. The title search is usually conducted by a company that specializes in this activity.
This is a crucial part of the mortgage process.
If there is a claim against the title, this greatly complicates the mortgage process, or when you’re trying to refinancean existing mortgage.