The Area Director's role is defined in the District Leadership Handbook because the Area Director is part of District Leadership. As the handbook indicates, each Area Director is "the direct liaison between the District and the clubs".
Area Directors receive Area Director Training.
Area Directors generally serve for a term of one year (although they may be re-appointed for one succeeding term), and may get credit toward their Advanced Leadership Silver designation. Their duties are described in the District Leadership Handbook and include visiting clubs, creating Area Director's Club Visit Reports, and hosting Area Contests, among other things.
The handbook gives a list of resources that an Area Director may find useful. A new Area Director may also wish to confer with the outgoing Area Director to understand how each club in the Area is doing and which clubs may need District assistance.