<include>**/*.properties</include>

This is a wildcard pattern used in build tools like Ant or Maven to include all files with the ".properties" extension in all subdirectories of a specified directory.

For example, if you have the following file structure:

project/
├── src/
│   ├── main/
│   │   ├── resources/
│   │   │   ├── config.properties
│   │   │   ├── database.properties
│   │   │   └── ...
│   │   └── ...
│   └── test/
│       ├── resources/
│       │   ├── test.properties
│       │   └── ...
│       └── ...
├── ...
└── ...

Using the pattern `**/*.properties` in a build configuration file would match all files in the `resources` directories and their subdirectories, resulting in a list of files:

src/main/resources/config.properties
src/main/resources/database.properties
src/test/resources/test.properties

These files can then be used for various purposes, such as reading configuration values or providing test data.