DevOps: that hated buzzword designed to demand sysadmins that can program and do both for half the price.
But the concept of DevOps itself has real benefits, so let's look at them in depth.
Both Chef and Puppet are both programs to automate server operations. They use community-created cookbooks for anyone to use to automate installations of programs, maintenance, or scripts.
Puppet is a DevOps approach to mass server configuration.
We spend a lot of time building identical configurations on Debian servers. We might as well have a single server as the flagship and use it to automate update tasks.
Chef is another competing approach.