Hi and welcome to HCM.
is by fluid acumulation in testicles which comes from abdominal cavitiy. The cause is the same as for hernias
and size of hydrocele varfise depending in how long do you stand or do exercise. It cant pass spontaneosuly in most cases and surgical procdure should be done for permanent treatment.It cant burst,it just can be painful and unpleasant. It can be also aspirated by needle but this is just temporary treatment. WIsh you good health