An attorney who has attained board certification from an accredited group such as the National Board of Trial Advocacy has demonstrated that he or she meets or exceeds levels of professional excellence in a specialty area of law.
Those attorneys are able to market themselves as specialists in those specifics practice areas. The goal is true specialist proficiency – tested and approved by rigorous peer review – and not a marketing gimmick.
The NBTA maintains a directory of their board certified lawyers. Also most state bar websites feature those attorneys who apply for and receive certification though their state bar.