Debt securities which depend on a pool of underlying receivables. In ART these refer to insurance-linked securities.
Essentially, an ABS is a bond or note backed by financial assets other than real estate and mortgage-backed securities. This includes loans, leases, royalties and so on, and for investors is an alternative to investing in corporate debt.
An asset-backed security is typically taken to be a security whose income payments and hence value are derived from and collateralized by a specified pool of underlying assets, such as a catastrophe bond is typically sitting atop a basket of treasuries or other high security assets.