Web conferences allow users to attend 'virtual' meetings from all over world. All that's usually required is an Internet connection and software if a particular client is being used. Video conferencing will allow two-way audio and video so that participants can see and talk to people in real time. In many ways, it's reflective of technology glimpsed in future of videophones, but on a larger scale.
The effectiveness of videoconferences lies in ability of participants to observe and react to body language, facial expressions and intonations of voice. While web conferences are still limited somewhat in this feature.
Conversation is possible in both mediums, though it takes some experience with web conferencing to make it personal. Though it is true that web conferences are about dissemination of information and not socialization of individuals for business purposes.
There is an international standard for videoconferences and this allows diverse software to communicate easily. There is usually one standard location for a video conferencing server that takes in all information and then distributes it to other conference locations.
This can be expensive depending on number of connections. Also, hardware that this requires includes video cameras (or a web cam), microphone, and speakers in addition to P.C. hard line connections and hub server. Web conferences are limited by only requirement that an Internet connection be available.