Question

what are voluntary muscles ?

Answer 1

Voluntary muscles are those which work under the command of brain .its not a reflex action so its takes some time respond for voluntary muscles
to say it in more fine words muscle whose action is normally controlled by an individual's will ;
mainly skeletal muscle ,composed of parallel bundles straited ,multinucleate fibres 
etc..
for example if you want to do some exercise you muscles will work under your brain there fore they are voluntary muscles
in other words voluntary muscles are totally opposite to reflex actions

Answer 2

Voluntary muscles are the ones which are work under the control of brain.
Example: Riding a bicycle, Dancing etc.