This article describes what the difference is between strings and (Automatic Translation) characters on POEditor.
Strings
The number of strings is the metric we use to charge a user (if needed) for a subscription. The number of strings in your account is the sum of the terms and translations in all the projects hosted on your account.
Only the strings added to the projects hosted on your account are counted against your string limit. If you are contributing to a project hosted on another account, the strings you add to that project are counted against the limit of that project's owner.
The paid plans we offer are listed here. If you don't know what a string is, read here.
Automatic Translation Characters
The Automatic Translation feature uses the Google/Microsoft/DeepL API (depending on your preference) for machine translation. Since the Google/Microsoft/DeepL APIs are not free to use, we need to charge for the Automatic Translation feature.
You can share some of your Automatic Translation characters with another POEditor user as described here.