Fabric is a Python library designed to upload files to, and run shell commands on, a number of servers in parallel or serially. These commands are grouped in tasks (regular python functions) and specified in a 'fabfile.'
This is called remote automation, and the primary use case is deploying applications to multiple similar hosts.
Although it is easier to automate when the target hosts are similar, it is not a requirement and Fabric has features for working with heterogeneous hosts as well.
Once installed, you can run fab help to learn more about how to use Fabric.