"Fictitious Business Name" (FBN) and "Doing Business As" (DBA) are both terms used to describe the public registration of a made-up business name. The terms are used interchangeably, along with the term "Trade Name" or "trading as" on the legal sites I referenced for this post.
YOU DO NOT NEED A DBA OR FBN IN ORDER TO SELL HANDMADE JEWELRY.
According to the website Business.gov, if you are a sole proprietor, then the legal name of your business is your full name. In some states, you may even be allowed to be "Jane Smith Jewelry" or even "Smith Jewelry" if your name is Jane Smith, and you will not have to file a FBN.
But, in most cases, if you want to use any name other than your full name to sell jewelry, or use something else as your url, logo, letterhead or email, then you have to register the made up name with your state, county and/or city (requirements vary from place to place).
Business name registration: All state requirements
Filing your FBN/DBN gives you the right to advertise and open a business bank account under another name. You'll be able to use that business name when filing for permits, billing customers, paying taxes, and so on. However, it does not necessarily protect your business name from being used by someone else. THAT would be a trademark, and that's a different legal beast.
I do not use a DBA. My opinion is that artists use their own names, and retailers create fictitious biz names. Monet didn't called himself "Splashy Dots." Gustav Faberge wasn't "Eggstravaganza." Tiffany wasn't "Lamps R Us." I think when jewelry artists use a fake name, it creates a sort of psychological distance between themselves and what they create, and might set up the wrong impression in buyers. I'm told again and again by handmade jewelry artists that, even at craft shows and art exhibitions, customers often assume jewelry sellers are only retailers--not artists and creators.
On the flip side, though, if jewelry is only part of your biz and you also sell beads, fabric, etc., then I can see wanting to have a catch-all biz name. Or perhaps you are in business with a friend and need a name for your collaboration.
When I began selling jewelry online several years ago, my full name .com was already a porn site. Lucky me. So, I use my initials + "jewelry" to avoid any awkward confusion. However, my business cards, address labels and PayPal account are all in my real name. I have no bank accounts or permits under the name JLHjewelry.com.
Here are some really good articles on the topic:
Doing Business As (DBA) - Fictitious Business Name
When does a variation of my name become a fictitious business name?
Naming Your Business
North Carolina Certificate of Assumed Name Forms
Jen Hilton makes one-of-a-kind jewelry sold through her website JLHJewelry.com. She is the founder of the Triangle Jewelry Makers and is featured in the books "Steampunk Style Jewelry: Victorian, Fantasy, and Mechanical Necklaces, Bracelets, and Earrings" and "1000 Steampunk Creations: Neo-Victorian Fashion, Gear, and Art" available at Amazon and other booksellers.