As a contractor, you could operate as an individual (i.e. natural person) or you could set up a legal entity. When setting up a legal entity, you could choose if you want to set up a sole proprietorship, business, organisation or partnership. In summary, there are 5 entity types that you can choose from:

Here’s the list of countries where you are NOT allowed to operate as individuals to be a contractor (to be updated in the coming weeks):

I have registered a legal entity, but I don’t know if that is considered a sole proprietorship or business?

Please check this page to see the local structures in your country.