A Community Manager is a person who has an innate drive to contribute to the community's prosperity. A community manager serves as a link between the organisation and its community, overcoming obstacles as they arise—or even before they arise!—by collaborating with other departments and the community to find solutions that benefit the entire community.
Layer5 Community Managers generally oversee community activities and support ongoing initiatives. They are responsible for the health and growth of the community. Community Managers cultivate an environment which attracts new community members by ensuring that timely and completed responses are provided to questions asked. Aspects of marketing including member and project promotion as well as aspects of project management by organizing meetings and triaging issues are under the purview of Community Managers.
Community Managers work to ensure that existing community members are retained by helping those members stay engaged in projects on an ongoing basis.
Take a look at the Community Handbook