Creating and managing security groups

EC2 security groups are virtual firewalls, which control inbound and outbound traffic to and from our EC2 Instance. We will create security groups before an EC2 Instance because this resource is required for creating an EC2 instance. Security groups and EC2 instances have many-to-many relationships. We can have a single instance with multiple security groups and a single security group can be applied to multiple instances, even multiple AWS instances present in the same subnet can have different security groups.