grails - What is the difference between BuildConfig.groovy and Config.groovy? -

i have grails app. why properties work in 1 not other? when put properties in 1 , when put them in other one?

from grails doc here

the first, buildconfig.groovy, settings used when running grails commands, such compile, doc, etc. second file, config.groovy, settings used when application running. means config.groovy packaged application, buildconfig.groovy not.