A capacitor is a component, that discharges and charges, while circuits are on (charged) or off (discharged).
450V 40uF Run Start Capacitor
Capacitors in a Bank[]
Sometimes, capacitors can be on a bank, by in Microfarads (uF), but they may take a while to charge them in a bank while the power is on.
A ABB high voltage capacitor bank.
Capacitor Plague[]
Capacitor plague was a phenomena witch caused higher than expected premature failure rate of aluminum electrolytic capacitors with non-solid or liquid electrolyte of certain brands, especially from some Taiwanese manufacturers. The capacitors fail because of a special water based corrosion effect, due to a poorly formulated electrolyte. When this happens the capacitor expands and bursts.
Many consumer electronics have been affected by capacitor plague most notably, computers, some of which are still being used today.
A cluster of capacitors affected by capacitor plague