A webcam was a device linked to and/or part of a computer which allowed people to communicate visually, as well as with audio.
The Doctor's allies communicated via webcam in his absence, with the exception of Wilfred Mott and Rose Tyler. Sylvia would not allow Wilf a webcam because she thought them "naughty." (TV: The Stolen Earth)
Sarah Jane Smith used a webcam to keep in touch with her adoptive son, Luke, while he was at university. (TV: Death of the Doctor)