What's the difference between BeanFactoryPostProcessor and BeanPostProcessor?

A BeanFactoryPostProcessor runs BEFORE any bean is instantiated, operating on bean DEFINITIONS (metadata) — PropertySourcesPlaceholderConfigurer, which resolves ${...} placeholders, is a classic example. A BeanPostProcessor runs AFTER each bean is instantiated, wrapping its initialization via postProcessBeforeInitialization()/postProcessAfterInitialization() — this is exactly how AOP proxies for @Transactional and @Cacheable get created, by replacing the raw bean instance with a proxy during this phase.