What a container search is
A container search is a set of closed containers placed on the floor or ground. Boxes are the classic choice. Depending on the sport and level, you may also see bags, cases, or other objects. The target odor is inside or on one of them, and sometimes none holds odor at all.
Your dog has to sniff each one, decide which smells like the target, and tell you. You do not know where the hide is. That is the point. Your job is to follow your dog and read their body.
Both AKC Scent Work and NACSW Nose Work use container searches, and the number of containers and the time limit change with the level. Check the current rulebook for the exact numbers. They get updated.