VCV is an open-source digital modular synthesizer - and a very nice piece of software. Modular synthesizers are about creating sounds, rather than just music - you start with a signal from an oscillator, add a shaped envelope to the sound, filter it (removing high or low notes) and finally add effects. Different oscillators can produce different signals - a sinewave sounds smooth, a sawtooth much harsher - and you can add or subtract other signals and add harmonics.
What VCV does well is provide an almost endless list of modules - over two thousand - each of which does at least one job. You hook them together with (virtual) patch cables, send the output to your speakers, and choose something like a MIDI keyboard or a sequencer module for your inputs.
My first good-enough track, an ambient-drone : SoundCloud
Heavily derivative of Building an Ambient Drone in VCV Rack by the wonderful Omri Cohen
Actually, playing with it again, it is an extraordinary piece of software. Visually gorgeous, UX is one of the best I’ve seen, and plays extraordinarily well with the modding / plugin community.
Various links
And then search up “Omri Cohen” on YouTube.