Maybe you see some simple Java program examples. Which JDK to use is based on the needs of the application, which is determined by the needs of the application. Contrary to you, most of the web projects I see use J2EE.
You have a problem
J2EE is based on J2SE
JDK is the core of the entire Java, including the Java Runtime Environment (Java Runtime Environment), a bunch of Java tools and Java-based class libraries (rt.jar)
JDK java development kit, J2SE java 2 standard edition, J2EE java 2 for enterprise edition,
JDK is a package of some basic methods provided by Sun. J2SE and J2EE are technologies used for different development.