In the earliest times of snipers, they go solo or alone to do the job compared to modern snipers. They were on their own to conceal themselves and avoid detection. After that, when the capacity of the sniper guns became better in covering distance and having better accuracy, snipers needed a partner to spot their targets. The partner, I think called spotter or scout, has the job of locating targets, measuring distance and wind velocity. This is crucial for the sniper to hit the target with just one shot. Missing the target could compromise their location. Snipers with partners are what have been shown on movies and other documentaries. It is not clear if the missions for a target involved two or more sniper teams.
The modern snipers are now a team composed of four to six members. The rationale is for the snipers to have more logistics, like food and ammunition, when assigned to a mission. Their training includes observing and mapping the target area. They also have to identify high-value targets especially when in a populated area. Keen observation of the snipers’ team is essential to minimize casualties in the process and this includes preventing casualties on their side. Another asset of the snipers’ team is to be able to blend to any type of surroundings they will be in.
Several modern snipers teams are assigned to a single target. They are to coordinate with each other on their moves. If necessary, there will be teams to penetrate the target area while other teams remain in the perimeters to monitor movements and security. Their mission ends only after accomplishing what needs to be done and they are able to return.