What is Spring? We cannot give a short answer. It's really tough to define Spring in a sentence or two. Many people may say Spring is a framework, but this would be also an understatement for Spring, as it may also be called a framework of frameworks. Spring provides you with a lot of tools, such as DI (dependency injection), IoC (Inversion of Control), and AOP (Aspect-oriented programming). While we can use Spring in almost any type of Java or Kotlin JVM application, it is most useful while developing web applications on top of the Java EE platform. Before moving into the details of Spring, we should first understand from where and why Spring originated and how it has evolved.