How do I manage my Ubuntu servers together?

What do server administrators use to send commands to multiple servers? I know what I’m describing has to exist, right?

For example, say I have 2 Ubuntu servers and they run on the same image, same users, groups, and everything. Only thing that is different is what websites I have setup under /var/www. I want to run “sudo apt-get update” and “sudo apt-get upgrade” on both of these servers. It would be awesome to have other options available too such as other commands, a system that is aware of the others too in my network.

Also, this would relate to having a load balancer, multiple servers of the same exact content. I would want them to all have the same commands executed on them at the same time.