1. App Web & Host Web
The special website to which the app is deployed is called an App Web.
The website to which the app is installed is called the Host Web.
例子：
Suppose, you are developing a SharePoint 2013 app for your organization. In that, you would require the App to access and to use the SharePoint components such as the lists, content types, workflows, and pages. In this Case, all your SharePoint components should be deployed in a separate SharePoint site, called as the App Web.
The Host Web is nothing but the SharePoint site where the App is actually installed. So, to conclude, all the resources accessed by a SharePoint web has to be deployed in a different site, named as the App web. And, the actual site where the app is deployed （from VS） is called the Host Web.
2. Client Authentication with Office 365
使用SharePointOnlineCredentials对象
ClientContext context = new ClientContext("https://gjq.sharepoint.com/");
System.Security.SecureString passWord = new System.Security.SecureString();
foreach (char c in "abcd1234%".ToCharArray())
{
passWord.AppendChar(c);
}
context.Credentials = new SharePointOnlineCredentials("cn0jacky@gjq.onmicrosoft.com", passWord);
3. App中的Client Web Part是否加入到Feature或者package中不影响App中的内容，App文件会将项目中的所有信息加入进去；
4.