Hi, Kontakt is available as a plugin hosted by a daw (digital audio workstation) like Reaper, Cubase, Ableton Live, Bitwig, Pro Tools etc.
Kontakt also provides a standalone version, no hosting ‘daw’ required.
Kontakt plays sound libraries created in it’s proprietary format, and allows editing/creating
of those sound librairies.
Spitfire is a competing product, with it’s own formats and capabilities, and various free
extended software, as a give-back to support musicians, sampling devotees, and sound designers.
vst and vsti are common plugin formats created by Steinberg (who supply Cubase daw)
Vsti are virtual instruments that provide sounds, Vst effects are used to surround those sounds at hand that are hosted on a daw track, (or in a standalone software app capable of hosting)
So you could have a daw like Reaper, hosting Kontakt, that in turn loaded sounds from various
library suppliers, and Spitfires competing plugin could be on a second track, also hosting
sounds, and you add more tracks to build your composition.
For narrating, you could create an audio track in reaper, and use a compressor plugin and reverb
plugin to dial in your voice, and this link will provide some quality videos on doing
voice-overs in Reaper…
youtube is LOADED with good Reaper-daw videos, for both newcomers, and pros alike! google search will find them. Welcome to the realm of virtual studio technology! And PianoBook!