Hey, Tasha!
Currently, Wix does not have a feature that would allow other people or businesses to sell their products on your site.
However, if you have a third-party app that allows this option, you can add it by embedding the HTML code .
You can also look for API of TPAs that suit your needs and work with them following the article https://support.wix.com/en/article/corvid-accessing-third-party-services-with-the-fetch-api
We have a section dedicated to integrations on our Examples page:
https://www.wix.com/corvid/examples?category=integrations