A vendor is defined as a supplier of goods or services. Normally, a vendor will sell the products or services to another company or individual. Vendor Field is also provided in field mapping. 
This part also provided some settings over there such as :

1. Append Prefix / Postfix on Feed

Appending the prefix/postfix on the feed will let you add some wording that you want to be added or updated for the product. It's supported by characters and symbols. 

For example:

A. Adding SKU: as Prefix in the vendor field


Value in feed
Result
CB34575
SKU: CB34575
AB645856
SKU: AB645856
Nike
SKU: Nike


B. Adding Collections as Postfix in the vendor field


Value in feed
Result
XES
XES Collections
Adidas
Adidas Collections
Nike
Nike Collections



2. Ignore Words

Ignore words lets you ignore the specific wording that you don't want to be added or updated for the product. Its supports multiple ignored words, separated by a comma while it also supports regular expressions too.