公有云和私有云

云计算提出的愿景，是要像用水用电那样使用IT服务，用户按需付费

云计算的三种模式：公有云、私有云和混合云

公有云——互联网上发布的共享的云计算服务，搭建云的资源在云服务提供商的场所内，所有用户共享公有云的基础设施资源。当同一时间使用云资源的用户增多时，资源会紧张
私有云——企业内部（专网）发布的云服务，搭建云平台所需的资源一般由企业自给；或者通过VPC实现

What is a public cloud? What is a private cloud?

A public cloud is shared cloud infrastructure. Multiple customers of the cloud vendor access that same infrastructure, although their data is not shared – just like every person in a restaurant orders from the same kitchen, but they get different dishes. Public cloud service providers include AWS, Google Cloud Platform, and Microsoft Azure, among others.

The technical term for multiple separate customers accessing the same cloud infrastructure is "multitenancy" (see What Is Multitenancy? to learn more).

公有云：共享云基础设施，不共享数据

A private cloud, however, is single-tenant. A private cloud is a cloud service that is exclusively offered to one organization. A virtual private cloud (VPC) is a private cloud within a public cloud; no one else shares the VPC with the VPC customer.

私有云：独享基础设施和数据

这篇文章以饭店为例，解释了公私有云的区别。https://www.cloudflare.com/zh-cn/learning/cloud/what-is-a-virtual-private-cloud/

VPC(virtual private cloud)

Virtual Private Cloud 是公有云上自定义的私有逻辑隔离网络空间

A virtual private cloud (VPC) is a secure, isolated private cloud hosted within a public cloud. VPC customers can run code, store data, host websites, and do anything else they could do in an ordinary private cloud, but the private cloud is hosted remotely by a public cloud provider.

与用户在数据中心运行的传统网络相似，托管在VPC内的是用户在私有云上的服务资源，如云主机、负载均衡、云数据库等。 用户可以自定义网段划分、IP地址和路由策略等，并通过安全组和网络ACL等实现多层安全防护

每个专有网络都由至少一个私网网段、一个路由器和至少一个交换机组成

路由器

路由器（vRouter）是专有网络的枢纽。作为专有网络中重要的功能组件，它可以连接专有网络内的各个交换机，同时也是连接专有网络和其他网络的网关设备。每个专有网络创建成功后，系统会自动创建一个路由器。每个路由器关联一张路由表。

交换机

交换机（vSwitch）是组成专有网络的基础网络设备，用来连接不同的云资源。创建专有网络后，您可以通过创建交换机为专有网络划分一个或多个子网。同一专有网络内的不同交换机之间内网互通。您可以将应用部署在不同可用区的交换机内，提高应用的可用性。