Client Access is a subset of Admin Access.  It is limited to only information which is related to the client and does not show Interpreter pay rates or agency sales.  The client can see his own invoices, if he is configured to permit that.  He can also schedule jobs within the time limits permitted as part of the customer configuration.  He cannot assign interpreters.  Here are some sample screens:
Below is the Dashboard the client sees.  All widgets only include information related to that customer and the sales widget is not visible on the lower right.

The Request tab looks same as for anyone with Scheduler authority.

The Interpreter tab only shows the assigned and/or preferred interpreter.  In this way the client can follow the assignment but not change it.

The Actuals tab only allows the client to see notes related to the job and the electronic signature if one was collected.