That page mentions "J2EE" just once, in reference to an API that hasn't been touched for years. But it does mention Java EE (JEE for short) multiple times, including the page name and the name of the main specification.
Which of the parts would you suggest for me ?
JDBC, JPA and servlets/JSP/JSTL for starters (and JAXP if you don't know that yet from Java SE). You can pick up other APIs as needed, like JavaMail, JAX-RS, JAXB, JMS, CDI, DI etc.