The Spring Framework is an open-source application framework for the Java platform. It provides comprehensive infrastructure support for developing Java applications, allowing developers to build robust and maintainable applications quickly. Spring offers features like dependency injection, aspect-oriented programming, transaction management, and more, making it a powerful tool for enterprise-level application development.

Dependency Injection (DI) is a design pattern used in the Spring Framework to implement Inversion of Control (IoC). It allows the creation of dependent objects outside of a class and provides those objects to a class in different ways. This promotes loose coupling and makes the code more modular and testable.

Spring supports Aspect-Oriented Programming (AOP) by allowing developers to define and apply aspects, which are modularized concerns that cut across multiple classes or methods, such as logging, transaction management, and security. Spring AOP allows you to declaratively define such aspects using annotations or XML configuration.

Spring Boot is a project built on top of the Spring Framework that simplifies the development of new Spring applications. It provides a set of conventions and defaults to quickly set up and run applications, without the need for extensive configuration. Spring Boot includes embedded servers, auto-configuration, and an opinionated approach to application development, which helps in creating production-ready applications with minimal effort.