About The Soft Pedal :
Pressing the soft pedal will make the note (s) played softer and quieter.

( Note: Due to the reason design of the electric piano keyboard itself in some models, the soft pedal function will not be obvious. it's not without this function, Even the original brand pedal unit is the same.
Such as P-125 and other models.This is mainly decided by the product design of the keyboards themselves.）
About The Sostenuto Pedal :
Selectively sustain, To sustain only certain notes.
Press piano key (s) down and then pressing the sostenuto pedal. At this time, the note (s) of the key (s) pressed will be sustained (even if the key (s) are released again) until the pedal is released, And the any note(s) played later will not be sustained after the pedal is pressed.
About The Sustain Pedal :
Pressing the sustain pedal, all the note (s) played will be sustained.