Automation is not the same as DSC and DevOps.

Automation is about changing existing process – to enable it start and work automatically, without human attendance, i.e. faster and more stable. The good example is site collection provisioning. 

DevOps is an idea to manage infrastructure configuration via code with well-known and proved developers practices – ADLC, version control etc. 

DSC is only one of many tools that allows SharePoint to be provisioned and managed via declarative CaC – Configuration as Code. You can think of provisioning SharePoint farm with DSC an automation too. 

Powershell is a scripting language that can be used for Automation (imperative way). DSC uses PowerShell syntax, but it is more than PowerShell.