A webcast is a media presentation distributed over the Internet using streaming media technology to distribute a single content source to many simultaneous listeners/viewers. A webcast may either be distributed live or on demand. Essentially, webcasting is “broadcasting” over the Internet.
Webcasting is also used extensively in the commercial sector for investor relations presentations (such as Annual General Meetings), in E-learning (to transmit seminars), and for related communications activities. However, webcasting does not bear much, if any, relationship to web conferencing, which is designed for many-to-many interaction.
Webcasting can also be used for other events where travel is prohibative such as weddings, anniversaries, retirements or funerals. Sample streams can be seen here