Creates a new security group.You can create either an EC2 security group (which works only with EC2),
or a VPC security group (which works only with Amazon Virtual Private Cloud). The two types of groups
have different capabilities
When you create a security group, you give it a friendly name of your choice.You can have an EC2
security group with the same name as a VPC security group (each group has a unique security group ID
separate from the name). Two standard groups can't have the same name, and two VPC groups can't
have the same name.
If you don't specify a security group when you launch an instance, the instance is launched into the default
security group. This group (and only this group) includes a default rule that gives the instances in the
group unrestricted network access to each other. You have a default EC2 security group for instances
you launch with EC2 (i.e., outside a VPC), and a default VPC security group for instances you launch in
your VPC.