Consigliere (Adviser) is an important position in a crime family. Considered as the third-most valuable position next to the Don, all of the Don's orders usually come through the Consigliere, although he holds no actual power.
The Consigliere is an adviser to the family and sometimes seen as the Boss's "right-hand man". They are often low profile gangsters that can be trusted. They are used as a mediator of disputes or representatives or aides in meetings with other families. They often keep the family looking as legitimate as possible and are sometimes, themselves, legitimate apart from some minor gambling or loan sharking. Some do not have crews of their own, but still wield great power in the family.
They are also often the liaison between the Don and important figures, such as politicians or Judges. A Consigliere's main job is to act as the Don's "auxiliary brain", helping the Don formulate plans. A Consigliere, by the very nature of his job, cannot afford to simply be a yes-man to the Don, and is one of the few in the family who can argue with the Don on family matters. When the Don comes up with a business plan, the consigliere has to constantly challenge that plan's weaknesses until it's foolproof.
The Consigliere is the only one in a family who knows all of the Don's contacts and secrets, and if made to talk, could bring an entire family to ruin. However, there is neither a future nor potential for profit in this, and so long as he keeps the faith, he and his family will continue to collect his rather substantial wages whether he is imprisoned or dead.
Consiglieres are usually viewed as civilians or foreign diplomats, and are not generally targeted by rival families. It is almost an unspoken rule that a Consigliere is a Sicilian, or at least an Italian, and always a trusted friend outside the Don's personal family.