What are the advantages and disadvantages of capacitors?

If you're talking about a capacitor for car audio related use, then I have the answer for you! :)

There is a lot of confusion in the industry about what the purpose of these are so I will get straight to the point.

Advantages: Capacitors reduce interference in the signal to your amplifiers therefore making your system cleaner. SQ cars use these typically. They can help with dimming lights but should be considered after an alternator and AGM battery are added as these are your best choices first.

Disadvantages: Capacitors actually reduce voltage slightly and interfere with direct current flow. As fast as they discharge they are almost useless in providing anything for long drawn out bass notes associated with rap etc.

*Note: Don't add one if you're already trying to consume more power than your charging system can produce. People use capacitors as a "band-aid"

to try and fix a bigger problem.