An FTL file is a template file used by FreeMarker, a template engine written in Java. FreeMarker is commonly used to generate text-based output, such as HTML web pages, configuration files, source code, emails, and more. The FTL file contains a combination of static text and FreeMarker Template Language (FTL) directives. These directives are special instructions that FreeMarker interprets to dynamically insert data, perform calculations, and control the flow of the template processing. When FreeMarker processes an FTL file, it combines the static text with data provided by the application to produce the final output. FTL files are often used in web applications to separate the presentation layer (the HTML) from the business logic (the Java code). This separation makes it easier to maintain and update the application. FTL files can include variables, expressions, loops, conditional statements, and other features that allow for complex and dynamic content generation. The FreeMarker engine replaces these directives with actual data at runtime, resulting in a customized output based on the input data.