Spring boot default initalization relativePath - maven

Question

I have used the spring boot initializer to generate a project.
What does this line do? Why is it used? What would happen if its not used?
<relativePath/> <!-- lookup parent from repository -->
An extract from The pom looks like this
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.rob.jpa.troubleshooting</groupId>
<artifactId>jpademo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>jpademo</name>
<description>Demo project for Spring Boot</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.4.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
...etc

Answer 1

It's the relative path from the module's pom.xml to the parent's pom.xml
(Ref: Maven Documentation)
In your case, its not required. because parent's pom is taken from JAR file.
Scenario :
If we have Application1 as parent to the module Application2, then we need to specifiy to locate the pom of Parent in the module's pom.xml