People come from various locations to one place to conduct a meeting.
These people normally work in the same building or, more likely, in a distant location and must travel to participate in the meeting. You can look at video conferencing as an electronic meeting where participants interact with other participants through the use of various pieces of video equipment. With a typical video conference, pictures and sound from one location are transmitted to one or more other locations by a camera and microphone. A codec is a specialized piece of equipment that compresses and converts the video signal from analog to digital and sends it over specific phone lines to the other video conferencing sites. The codec on the receiving end decompresses the incoming digitized images and converts them to their original form.