Commercial Mortgage-Backed Securities (CMBS)

What Does Commercial Mortgage-Backed Securities (CMBS) Mean?
A type of mortgage-backed security that is secured by the loan on a commercial property. A CMBS can provide liquidity to real estate investors and to commercial lenders. As with other types of MBS, the increased use of CMBS can be attributable to the rapid rise in real estate prices over the years.

Investopedia explains Commercial Mortgage-Backed Securities (CMBS)
Because they are not standardized, there are a lot of details associated CMBS that make them difficult to value. However, when compared to a residential mortgage-backed security (RMBS), a CMBS provides a lower degree of prepayment risk because commercial mortgages are most often set for a fixed term.