A .BSM file extension is associated with an 'SQLMatcher' project file.

SQLMatcher is a 'database schema comparison and synchronization utility', which essentially means that it compares data held in multiple databases.

The .BSM file contains information regarding and specialised options/scripts in addition to information about the data being compared.

SQL or 'Structured Query Language' is a database language, designed specifically for the management and retrieval of data within 'relational database management systems'.