SaaS: Email, Online Software, like Xero, Salesforce.com PaaS: Web code quick deploy portal or platform, like Google App Engine, Heroku, Github Pages IaaS: VM which can be configured OS, network, storage etc, like AWS EC2, Azure
SaaS：电子邮件，在线软件，如Xero，Salesforce.com PaaS：Web代码快速部署门户或平台，如Google App Engine，Heroku，Github Pages IaaS：可以配置操作系统，网络，存储等的VM，例如AWS EC2，Azure