Error while running Powershell script

Question

New-Object : Cannot find type [Microsoft.SharePoint.Client.ClientContext]: make sure the assembly containing this type is loaded.

+ $ctx = New-Object Microsoft.SharePoint.Client.ClientContext($siteURL)

+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

+ CategoryInfo : InvalidType: (:) [New-Object], PSArgumentException

+ FullyQualifiedErrorId : TypeNotFound,Microsoft.PowerShell.Commands.NewObjectCommand