File with a .SEAM extension contains a reference to a backing servlet, that is, a class of a Java server, processing HTTP requests of a network application. SEAM files are utilised in the JBoss Seam environment, in the JavaServer Facelets software.

Although the extension is being used, usually, when we refer to the *.seam term, it is not a physical file within server’s file system, but a type of servlets mapping, defined in a web.xml configuration file.