SBOM stands for Software Bill of Materials. It is a manifest of all the code in a system, device, or application including particular code and libraries from open source software, third parties, etc. It allows users to know what’s actually in an application, and thereby do security update, recalls, etc. in the same manner that is currently done for hardware like for medical and automotive.
In the USA there is an effort to better define common standards and methods around SBOM being headed by the NTIA. See https://www.ntia.gov/sbom