Apart from helping in bootstrapping application development, Spring Boot enables a number of features that can be used in the application. These additional features include, but are not limited to, monitoring and managing the application. Application management and monitoring can be done over HTTP endpoints or using JMX. Auditing, health checkups, and metrics can also be applied with a configuration in a Spring Boot application. These are the production-ready features provided by the spring-boot-actuator module.
Here is the definition of the Actuator from the Spring Boot reference documentation (https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#production-ready):