A pack walk is an important activity when you are trying to socialize dogs with each other.
When they are walking in a pack, they are actually working like a team.
They become a single pack at that moment which creates good association with each other and triggers the pack mentality which help them to get aquainted quickly when they meet next.
It drastically lowers the probability of a fight among them.
Walk should be structured, which means dog should be focused on the humans and human should be leading the walk.