The firm registers as a registered-investment-adviser; the humans who actually advise clients register separately as representatives, generally at state level even when the firm is SEC registered. Qualification usually means passing the series-65, or holding the series-7 plus series-66, or relying on a professional designation that some states accept.
An IAR inherits the firm's fiduciary-duty. Personal trading is monitored under the firm's code of ethics, outside business activities must be disclosed, and client complaints appear on the public record.
Someone can be both an IAR and a registered-representative of a broker-dealer. That dual-hat arrangement is legal but creates conflicts that must be disclosed, because the same person is paid two different ways for two different kinds of recommendation.
Related: registered-investment-adviser, series-65, series-66, fiduciary-duty, registered-representative