Further to OFs reply...
To achieve the full frame rate of a webcam - say 30fps a certain connection speed will be required.
At slower speeds the video cannot be transmitted at the speed that at which it is captured, which leads to much lower frame per second (fps) rate, say 1fps when using a connection such as dial-up, and depending on the video resolution of the webcam and the program being used.
All the same, whilst video may be anything but smooth, it should appear correctly and be fully legible.