This is a tremolo effect with several nice features. The OLED screen will show the actual characteristics of the amplitude modulation waveform. 
'Level': Adjust extra gain
'Freq': Set the tempo
'Depth': Adjust the depth of the modulation
'Shape': AChange the modulation waveform; sine,sawtooth, inv sawtooth, square or triangle
'Tap ratio': Change the ratio when you use Tap tempo
'Stereo mode': In stereo you will have a Ping-pong effect

You can use the Ratio switch to change the tempo in relationship to the tapping.
2:1 will double the tempo
1:2 will half the tempo
3:2 will give a triplet feeling and so on..

It is both stereo input and output. But then you of course need a splitter.
No problem to use it with a mono cable if you don't need that fancy stereo thing.
It is also possible to connect an expression pedal to both control the frequency and the depth of the tremolo.
You can use a standard expression pedal like Roland EV-5
Tip: Signal
Ring: High
Sleeve: Low

SPECS: 
Power: 9V negative center 200mA
Max input level: 2.8Vp-p
Input imp: 500kOhm
Out imp: 1kOhm