Counsel, in simple terms, refers to an attorney, lawyer, counselor, barrister, solicitor, attorney at law, proctor, or an advocate who holds the license to practice law. Under Unites States law, they are all same.
The counsel can take shape of one or more lawyers representing a client. Their duty is to give legal advice to the client which a client may decide to act upon or ignore. It is actually a description given to any attorney who is not the in-charge or principal lawyer of the case.