I can't find a good official Microsoft reference anymore for using CSOM with PowerShell for SharePoint Online.
Working with PowerShell is slightly different then: JavaScript API reference for SharePoint REST API reference for SharePoint .NET server API reference for SharePoint .NET client API reference for SharePoint
Like here: https://msdn.microsoft.com/en-us/library/jj162979.aspx
And here: https://msdn.microsoft.com/en-us/library/ee537855(v=office.14).aspx