A hydrocele is a common finding of fluid in the scrotum around the testis. It is generally self-resolving and requires no active management.
It is important not to confuse a hydrocele with an acute scrotal swelling - see the Royal Children's Hospital clinical practice guidelines.
It is important to distinguish a hydrocele from an inguinal hernia, with the latter being reducible (unless incarcerated) and compressible. You are not generally able to get above an inguinal hernia with palpation. Note that a hydrocele may sometimes be very slowly compressible, although never rapidly compressible.