Get-ADObject giving errors

I have a little bit of knowledge in using PowerShell but have very long way to go.  I am trying to use the Get-ADObject command but having problems. 

Using this command(also with all possible parameters i can think off):

Get-ADObject -Identity $user -Server $domain -Credential $myCred

I get an error saying: Get-ADObject : Cannot find an object with identity: 'user' under: 'domain'

Now if use: Get-ADUser -Identity $user -Server $domain -Credential $myCred

it goes through fine with no problems and bring the result back.

any suggestions???