Maven Properties:

You can define the custom properties and that can be reused in the respective tags.
That makes the pom.xml more easy to read.
You can say properties are place-holder and that can be easily used in the scope of
pom.xml file using the ${property-name} syntax.

Here, when you need to upgrade the version of spring then just only change the value in the
 <spring.version> tag only.

<properties>
    <spring.version>4.2.0.RELEASE</spring.version>
</properties>

<dependencies>    
<dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>${spring.version}</version>
    </dependency>
</dependencies>