Mortgage-backed securities (MBS) are a key concept that is central to Freddie Mac's work. Regardless of which role you have applied to, make sure you have at least a basic understanding of the concept and Freddie Mac's relationship to it. MBS are assets that are secured, or backed by, home loans and other kinds of real estate loans. Freddie Mac divides mortgage-backed loans up by tranche and then sells them on the open market. You may have encountered these types of securities in previous roles, or you might not have worked with them at all. Either is OK, so long as you demonstrate that you've done your homework and can speak confidently about MBS and other industry-relevant concepts.