There is an error "This root certificate is not trusted" in my Keychain Access.
What is "Apple Configurator"? And what should I do about this error?
Apple Configurator is a piece of software from Apple that allows you to centralized manage multiple iOS devices (e.g. remote wipe, remote software rollout,...). It's made mostly for companies, organisations,schools, etc.
To be able to help you with the certificate you need to post the certificate details.