Quick Answer: LN Live is a feature that allows you to improvise error-free to a melody via a QWERTY computer keyboard or a MIDI input device (e.g. keyboard).
LN LiveLiquid Notes is equipped with a feature for improvising and creating melodies, called LN Live. With it, you can improvise error-free - i.e. only correct notes will be played - via a QWERTY computer keyboard or a MIDI input device (e.g. keyboard).
Any note played will illuminate the Note In indicator at the bottom right of the Liquid Notes window *:
LN Live will automatically select the correct scale for chord regions while a song is playing, and map wrong notes you play to the right notes in accordance with the Input Scale settings you selected.
You can select the Input Scale under Settings > LN Live > Input Scale > Keynote.
*: If a MIDI input device is connected, you can check it's connection status via the Note In indicator. Also, the Current Scale of your arrangement for the respective cursor/playback position and Bypass is shown there.