That depends on how the action is configured. The OneDrive action step has properties to define the file name and path within OneDrive to send the file.
If you are using the default Save to OneDrive action that ships in the “Basic” action group, it is configured a blank value for “path”, so will place the file in your “default” folder in OneDrive. The concept of the default folder is a bit weird, and can vary for different types of accounts, but usually is the same as the “My Files” folder in the sidebar if you are looking at your OneDrive on the website
The action has a file name template of [[time]].txt, which gets evaluated to a Y-M-D-H-M-S timestamp at the time the action is run – so would come out with a file name something like 2020-01-15-08-06-19.txt.
Hopefully that makes sense. You can edit the action (or make copies of it for different purposes) and alter those values, like putting “Drafts” in the folder path to send to a folder named “Drafts” in your account…or use [[safe_title]] in the file name to get a name based on the first line of the draft. You can learn more about using those options in this template basics article.