Capacitors?

Question

what are the uses of coupling capacitors? decoupling capacitors? smoothing capacitors? and its use as a timing element? and other attributes of capacitor..

Answer 1

A capacitor is a reactive device, not resistive.  It's not measured in resistance but in impedance.  It may have some high resistive value but this is not it's major effect.  

A capacitor in series can couple an AC signal from point A to point B while blocking DC.  A capacitor from some point to ground can remove or reduce an AC component from that point.  This filters or "smooths" the signal.  A capacitor and resistor circuit will have  a specific time constant (TC) to charge or discharge and can provide timing signals.  A capacitor will also produce a condition where the current leads the voltage by some degree.