A registered trade name that allows a business to operate under a name other than its legal entity name.
A DBA (Doing Business As), also called a fictitious business name or trade name, lets you operate your business under a name different from your legal entity name. For example, if your LLC is registered as "Smith Consulting LLC" but you want to operate as "Apex Strategy," you'd file a DBA for "Apex Strategy."
DBAs are registered with your county or state (requirements vary) and are typically inexpensive ($10–$100). They're required before you can open a bank account under a trade name and in many jurisdictions before you can advertise or do business under the trade name.
A DBA doesn't create a separate legal entity — it's just a name. Your LLC or corporation is still the legal entity that owns the business and enters contracts. The DBA is just the sign on the door. Also important: registering a DBA doesn't give you trademark rights to that name. If you want to protect a business name, you need to file a trademark with the USPTO.