Network Access Control Lists (ACLs) are an essential component of AWS. They provide a way to secure network traffic by allowing the customer to specify which traffic is allowed on their AWS cloud instances, and which should be blocked. Through the use of rules and conditions, ACLs provide granular control over inbound and outbound traffic. Network ACLs are stateless; they do not manage connections or sessions but rather act as a packet filter. They are applied at the subnet level, allowing customers to create different sets of rules for different parts of their network. Network ACLs can be used in conjunction with security groups for extra protection against malicious activity or unauthorised access.