server.port=8081
spring.datasource.url=jdbc:mysql://localhost:3306/demo
spring.datasource.username=root
spring.datasource.password=secret
spring.jpa.hibernate.ddl-auto=update
logging.level.org.springframework=INFO

• application.yml is the same idea with YAML's nested, indentation-based syntax
• Values can be read back with @Value("${server.port}") or a @ConfigurationProperties class
• Profile-specific files (application-dev.properties) override the base file per environment