X-Y panel: X controls speed, Y controls LowPass Filter and volume optionally.
Mode: "Pitched" means the wave will be resampled as speed is being modulated; "Grainy" means the wave will not change pitch but the grains will change size as speed is being modulated.
Sync mode: "BPM" or "Free".
Note subdivision selector.
Y->Vol (Y value to Volume) button.
Zero - X: Useful only in "Grainy" mode; this parameter is useful to avoid clicks, but if you want to go very fast you better untick this option, otherwise you'll hear an artifact in where the pitch transitions aren't smooth on very high frequencies.
X and Y spring buttons: Enable disable spring release on them.
Smooth knob: This smoothes out the X and Y values, high values result on slow response to quick movements, useful to make slow sweeps such as on one famous Daft Punk song.
Grain size knob: When in "Free" mode (opposed to BPM) you can specify the grain size here.