Debconf without capital 'C' is a system used to configure Debian packages. Debconf gives users as fine a degree of control during configuration as they choose.
Linux.com has an article on the tool
Every part of a Debian system is not configurable through Debconf. For example, the Advanced Linux Sound Architecture (ALSA), which delivers sound to the desktop, has its own configuration tool called alsaconf for selecting a driver for a sound-card — although, confusingly, the basic alsa package itself has a setting that can be configured through Debconf. Nor is the Common Unix Printing System (CUPS) configurable through Debconf. Hess notes that Debconf is currently not ideal for partitioning, installation programs, or large-scale installs either, although he hopes that recent efforts to extend it “will eventually make Debconf more usable for these types of configuration.” Moreover, for desktop users, Debconf may be increasingly replaced by graphical tools that are even easier to use.