What is the difference between "00-installer-config.yaml" and "50-cloud-init.yaml"

I have multiple Ubuntu 18.04 and Ubuntu 20.04 servers (some upgrades, some fresh installs) running on Hyper-V, Raspberry Pis, and the cloud. I have noticed that for configuring netplan, directory /etc/netplan sometimes contains 00-installer-config.yaml file, and other times 50-cloud-init.yaml file. The content and syntax on both is usually the same so why is the file name different?