Common Law Rights

If you do not own a federal (or state) trademark registration for a mark, any rights you have will only exist at common law in your geographic area of use (which may also include a zone of natural expansion). Thus, if Company A uses the mark FIERCE TRACTION to sell clothing in Florida and Georgia and Company B (not knowing of Company A) adopts the same mark to sell clothing in California, both Company A and Company B could each have rights in the same trademark in their geographic areas of use. 

On the other hand, a federal trademark registration will generally give you nationwide priority starting from the date your application was filed. This provides you with prior rights over anyone who — after your filing date — first starts using, or applies for registration on an intent to use basis, a mark that is likely to cause confusion confusion with respect to your mark.