One example to understand it, if someone finds it useful, is the following:
Most QKD is done by sending light through a channel. In DV-QKD we send single photons through the channel, one at a time. We encode the information, for instance, in the polarization of each photon. In CV-QKD we send a continuous beam of light, as in most classical optical communications. The information can be encoded, for instance, by modulating the amplitude and phase of the electromagnetic wave.
The first QKD protocols were DV, as the BB84 protocol (1984). CV-QKD protocols were proposed in the 2000s. So the article's year of publication may give you a clue. I would say that if someone is just introducing the concept of QKD (as in an undergraduate course) he would be referring to DV-QKD rather than CV-QKD.