A Market Place is a website which enables you to purchase product(s) from more then one seller. The typical Market Places which most of us are familiar with in the UK are Amazon, eBay and Rakuten. All these market places are also in countries around the World so once you have mastered the UK market there’s no need to stop there.
Many businesses now trade on market places as well as their own websites for a number of reasons…but it’s not for everyone. More importantly these market places should be used to benefit ‘your’ business and not theirs. With that last comment in mind, if they had their way you would have all your products on their site, which isn’t always best for you.