The Matrix can produce three types of output: Curve CV, Note (Key) CV and Gate CV.
Note CV normally controls note pitch.
When connected to an instrument device Sequencer Control input, the values correspond to semitone steps. The Note CV values are shown in the upper part of the Matrix display, if the "Keys" mode is selected.
Gate CV represents a note-on/off value, plus a level value (that could be likened to velocity).
The Gate values are shown in the lower part of the Matrix display.
Both of these two outputs are typically connected to the Sequencer Control Gate and CV inputs on a compatible instrument device. For example, if you create a Matrix with either a synthesizer (Subtractor, Malström) or a sampler (NN-19, NN-XT) selected, they will be auto-routed in this way, and will control one voice in the device.
Curve CV is a separate pattern, programmed separately from the Note/Key and Gate CV.
The Curve CV values are shown in the upper part of the Matrix display, if the "Curve" mode is selected.
This is useful for programming CV curves that control other parameters other than note pitch (although you could do this too). This way you could control the note pitch and triggering from the Key and Gate outputs for a device, then add a second independent pattern using the Curve CV output that could control filter cutoff for example.
It should be stressed that all three outputs can be used in any number of ways. For example, you could use the Gate CV to trigger a drum in Redrum, or let the Curve CV control the feedback parameter of a delay, etc.