The job of a buffer pedal is to preserve the strength of your input signal by boosting it. Going through multiple pedals in low-level signal situations tends to compromise the high-end fidelity of the signal. Therefore, a buffer pedal is used to restore the capacitance that was lost while the signal was traveling through other pedals in your signal chain. Buffers are suggested to be placed after certain pedals, such as fuzz pedals and kept closely following overdrive pedals.