e.g. you have different environments (test, dev, prod) you can add different application.properties files and configure thing differently among the environments. lets say you want to change the logging behavior on test env to trace, but in prod to be info. you can add a application-test.properties and application-prod.properties to the project and define the spring.profile.active in the “parent” application.properties file. the active profiles properties files has higher priority but the default config is loaded as well. if there are 2 configurations for 1 thing the one with the higher prio is chosen.