Velocity Sense

This control defines how much the velocity coming off your MIDI device affects clip's volume. At 0%, which is the default, it doesn't matter how hard you press a key or a pad, the volume will be what you set it to. At 100%, hitting a key as hard as you can produces maximum volume, and pressing the key or a pad really softly produces a barely audible sound.

Launch Style

The Launch Style defines how you interact with the clip's playback. Ardour makes a distinction between pressing a button or a key (the 'down' event for a mouse or the note-on MIDI event) and releasing a button or a key (the 'up' event for a mouse or the note-off MIDI event).

You can setup a trigger slot so that you would press a silicon pad on your external grid controller, and Ardour would play the clip in that slot indefinitely on repeat. Or you could set it up so that it would only repeat that clip as long as you are keeping the pad pressed and stop playing it as soon as you stop pressing the pad.

Trigger Clicking will trigger the playback of a clip. Further clicks, as well as mouse up and note-off events will be ignored.
Retrigger Clicking will trigger the playback of a clip. Another click will restart (retrigger) the playback from the beginning, quantization will be taken into consideration. Mouse up and note-off events will be ignored.
Gate The clip will be played back as long as you keep the mouse button or the MIDI key/pad pressed. Quantization defines how soon playback starts after pressing the button/key down and ends after releasing the button/key.
Toggle The clip will keep playing until you click the button again or send another note-on event from your MIDI device
Repeat The contents of the clip will be played to the extent of the quantization setting.

Launch Quantize

This setting defines how long Ardour will wait till beginning the playback of a clip in a trigger slot. If the transport is already rolling, and quantization is set to 1 bar, which is the default, Ardour will wait for the next bar, then start playing the clip. Quantizing to a whole bar or several bars typically guarantees that downbeats of a drums track and a bassline track align.

The quantization value can be as large as 4 bars and as small as 1/64 bar. When 'None' is selected, playback with a rolling transport will start immediately.

Legato

The Legato mode helps keeping two clips of the same track in sync when you switch from one to another. With Legato on, Ardour will pick up the playback of the second clip at the position where the first one left off. Please note that quantization applies here.

Cue Isolate

FIXME, If selected, the slot will not respond to start/stop cue events (does it work?)

Follow Options

FIXME. These options are where you define the transition from one slot to another.