Sets a property pointing to the artifact file for each selected project dependency. Each property name will have a base name in form of groupId:artifactId:type:[classifier][.relative][.suffix]. This is similar to the dependency:properties goal but with additional features, like filtering and relative paths.
Basically it sets a property which value is the path to a artifact of a dependency:
junit:junit:jar=/home/user/.m2/repository/junit/junit/4.8.2/junit-4.8.2.jar
or
junit:junit:jar.relative=../../../.m2/repository/junit/junit/4.8.2/junit-4.8.2.jar
For usage, click here.