dnd 5e – If the group is hidden before attacking enemies, do they surprise the enemies and / or gain advantage in their attacks?

Our skilful heroes tracked the goblins back to a small camp in the woods. Completely unaware of the threat that surrounded them, the goblins sit around a fire, easy prey of the hidden band of adventurers lurking in the trees.

The party attacks! Arrows fall, spells are cast and those who wield the sword come running. Our group:

  • Attacks with advantage because they are hidden?
  • You only get a surprise round to catch the unconscious goblins?
  • Do you have as much surprise as an advantage?

What are the scenarios in which each of the above would occur?