The Java EE platform is built on top of the Java SE platform, but they are not released together.
For instance, both Java EE 8 and Java SE 9 were released on 21st September 2017. But Java EE 8 requires Java SE 8 that released on 18th March 2014.
The Java SE platform
The Java SE platform provides the core functionality of the Java programming language. It defines everything from the basic types and objects of the Java programming language to high-level classes that are used for networking, security, database access and XML parsing.
In addition to the core API, the Java SE platform consists of a virtual machine, development tools, deployment technologies, and other class libraries and toolkits commonly used in Java technology applications.
The Java EE platform
The Java EE platform is built on top of the Java SE platform and provides an API and runtime environment for developing and running large-scale, multi-tiered, scalable, reliable, and secure network applications.
Since September 2017 the Java EE 8 API artifacts are available on Maven:
Java EE 8 Platform
<dependency>
<groupId>javax</groupId>
<artifactId>javaee-api</artifactId>
<version>8.0</version>
<scope>provided</scope>
</dependency>
Java EE 8 Web Profile
<dependency>
<groupId>javax</groupId>
<artifactId>javaee-web-api</artifactId>
<version>8.0</version>
<scope>provided</scope>
</dependency>