Kontakt and Soundpaint are both Sample Engines: software that hosts sample libraries and virtual instruments. Both engines run as plugins in your DAW (Digital Audio Workstation). You might also hear plugins referred to as VST, AU, and AAX - which are different plugin formats for different DAWs. Both Kontakt and Soundpaint are available in all 3 of these plugin formats (note: AU is Mac only, and AAX is only for Pro Tools).
8Dio instruments run in and require Kontakt, created by Native Instruments. Kontakt is an industry standard, tried and true, and must be purchased separately from Native Instruments.
We have developed hundreds of instruments for Kontakt, and while we love all of these instruments, we also wanted to do more. That's why we created Soundpaint, a new sample engine for a new generation of instruments. From ultra deep-sampled synths to innovative strings and custom instruments, Soundpaint takes sample instruments to the next level with even more emotional realism, customization, sound design options, and speed. It's also free, so you only need to buy the instruments (or pick up some for free).
Soundpaint also comes with a Free Sample Editor that lets your import your own samples with just a single click.