If selected, this allows you to define a variable - Jenkins.Repository - that will be present in the Maven environment that points to the specified repository.
The best way of using this is to create a profile in the Jenkins settings.xml:

        <profile>
            <id>jenkins</id>
            <repositories>
                <repository>
                    <id>jenkins</id>
                    <url>${Jenkins.Repository}</url>
                    <releases>
                        <enabled>true</enabled>
                    </releases>
                    <snapshots>
                        <enabled>true</enabled>
                    </snapshots>
                </repository>
            </repositories>
            <pluginRepositories>
                <pluginRepository>
                    <id>jenkins</id>
                    <url>${Jenkins.Repository}</url>
                    <releases>
                        <enabled>true</enabled>
                    </releases>
                    <snapshots>
                        <enabled>true</enabled>
                    </snapshots>
                </pluginRepository>
            </pluginRepositories>
        </profile>

    

This profile is then enabled by adding "-Pjenkins" to your maven build options.