There may not be a difference.  This is just like the customer list.

It depends on the vendor and how you work with them.  E.g. for a sole proprietor you might know them by their personal name, but then also want to enter their legal name in the company name field, perhaps for tax reasons to issue a 1099.

For example, in my company I use my customer's personal name as the customer name and so the Company name is usually different, and the FML fields are more or less the same as the customer name.