Independent contractors have many names: gig workers, freelancers, contingent workers, contract hires, 1099ers, the alternative workforce... the list goes on.
This type of work can span industry, function, experience level, and geographic distance. One thing that ties these people together is the 1099-MISC form. It's a US Government form that is issued to you by the person who's paying you (often a client/customer). It helps track income that you've made with Uncle Sam. There are other types of 1099, but they're much less common.
Having a 1099 means that taxes aren't withheld from the payments you receive as income. It also means that you usually have more autonomy in when and how you work, and you typically don't have access to benefits from an employer.