Salt, like Ansible, is a response to the Puppet/Chef hegemony -- ruby and DSL's and tacked-together bits that are a nightmare to install and upgrade in themselves).

I'd suggest Salt did some things much cleaner than Ansible, and while it can be an orchestrator, and deployment system, it also excels as a configuration management system ... but I think typically people are talking about configuration management systems that are tightly coupled with more formal change management systems (of which I've found pretty much none that work well).