The localhost account is used to migrate your local development website and files from your computer.
Which information do I need to create a localhost account?
You will need your local website URL exactly as you have from the browser, for example:
Together with the website URL, you will need the document root of your website, ie the folder on your computer where you store all the files for your website.
If your website uses a database (WordPress site for example), you will need to add the database name of your website.
After entering all the information on your localhost account, you can check if the information you entered is valid, and the Migrate app identified all the necessary data to proceed.