Salt and Puppet are useful for managing a fleet of servers running various applications, especially when you need to scale those applications horizontally or want geo-distribution.

Ansible can also do that, on top of literally anything else you could want - network configuration, infrastructure automation, deployment pipelines, migrations, anything. As always, that flexibility can be a blessing or a curse, but I think Ansible manages it well because it's so KISS.

RedHat's commercial Ansible Automation Platform gives you more power for when you need it, but you don't need it starting out.