With the minimal information you give us it is impossible to give a definitive answer, but anyway:
.ctl is the default file-extension for Oracles SQL*Loader. For this product the WHEN clause specifies wheter a record is loaded or not (in this case the first 2 characters match 02).
This
link points to the Oracle documentation. The WHEN clause is described there and it may help you to verify if the examined file is a control file for SQL*Loader.