Hello and welcome and I'm going to be talking to you about VPCs. Virtual Private Clouds. Now to understand what a VPC is, let's just take a look at the AWS infrastructure. 

So, here is the AWS Cloud. Very simple. And a VPC resides inside of the AWS Cloud and it's essentially your own isolated segment of the AWS Cloud itself, so here is your VPC sitting inside the AWS Cloud. 

Now by default when you create your VPC, the only person that has access to this is your own AWS account, just you. It is totally isolated and no one else can gain access to your VPC other than your own AWS account. Now obviously there are millions upon millions of other VPCs within the AWS network created by other customers all across the world. So, there are millions of customer VPCs. However, they do not have access to your VPC and likewise, you do not have access to their VPC. 

Now what do you use a VPC for? Well, essentially it allows you to start deploying resources within your VPC, for example, different compute resources or storage or database and other network infrastructure among others and this allows you to start building and deploying your solutions within the Cloud. 

Now by default from a limitation perspective, you are allowed up to five VPCs per region per AWS account and it's very simple to create a VPC. All you need to do is to give it a name, when you create your VPC and also define an IP address range that the VPC can use and this is done in the form of a CIDR block which stands for Classless Inter-Domain Routing. And I'll talk more about that when I talk more about subnets in a few minutes. 

So, just to recap at a high level, simply put, a VPC is an isolated segment of the AWS public cloud that allows you to provision and deploy resources in a safe and secure manner. I now want to dive deeper into the VPC architecture and start talking about subnets and how you can segment your VPC out into different areas across multiple availability zones for resiliency and high availability, so let's take a look.