Yahoo! Groups is one of the world’s largest collections of online discussion boards. The term Groups refers to Internet communication which is a hybrid between an electronic mailing list and a threaded Internet forum, in other words, Group messages can be read and posted by e-mail or on the Group's webpage like a web forum. In addition, members can choose whether to receive individual, daily digest or Special Delivery e-mails, or simply read Group posts on the Group’s web site. Groups can be created with public or member-only access. Some Groups are simply announcement bulletin boards, to which only the Group moderators can post, while others are discussion forums. The variations of Yahoo Groups are virtually endless.
As well as providing e-mail relaying and archiving facilities for the many Groups it hosts, the Yahoo! Groups service provides additional facilities for each Group web site, such as a homepage, message archive, polls, calendar announcements, files, photos, database functions, and bookmarks.
It is not necessary to register with Yahoo! in order to participate in Yahoo Groups. The basic mailing list functionality is available to any e-mail address, but a Yahoo! ID is required to access some other features.