I've seen this syntax in many places, such as when using javscript, thymeleaf(spring), properties files etc.//ex; in properties file. Where are the values coming from? ${someText}  ${set.config.username}What is ${} actually called? I am trying to do research on understanding where the values are coming from when it is in the curly brackets. But when I google ${} relevant suggestions show up. I would need the actual name of this so I can get more crisp information on it.
What is this command called?
spring;properties
I think the phrase you are looking for here is string interpolation or variable interpolation. Basically, something (whatever is processing or pre-processing the properties file in this example) should replace ${someText} with the value that is defined elsewhere (by user input, by an environment-specific config, something else...), probably in the form someText=blah blah blah.