CiviCRM is an open source CRM (constituent relationship management) system that expands the functionality of your website in many different ways.
CiviCRM is a powerful, web-based contact relationship management (CRM) system. It allows an organisation to record and manage information about the various people and organizations it interacts with. CiviCRM is more than just an address book, it also allows you to track your interactions with people and organizations, engage with constituents, and solicit donations through your website. The information you gather is all stored in one place but you can access it from almost anywhere.
CiviCRM focuses on the needs of non-profits. CiviCRM emphasizes communicating with individuals, community engagement, activism, outreach, managing contributions, and managing memberships.
The above (from the free online user guide) is a good introduction to CiviCRM. We're happy to discuss your organization's needs and whether CiviCRM could be a solution for you. It has six optional components for case management, fundraising, event registration, membership management, email blasts, and report generation. One of the huge benefits not mentioned above is the tight integration with Backdrop CMS, Drupal, Wordpress, and Joomla).