Interim, is what we all understand as - during the pendency of proceedings.
Any order would only be passed after hearing the other side and that also applies to interim orders.
However, in a gross case to avoid miscarriage of justice and to prevent the proceedings from getting infructuous, some orders may be passed at the time of issuing notice to the other side. Such orders are subject to the contentions of other side that may be raised on the first returnable date. If the other side is able to convince the court as to necessity for vacating ad-interim relief on the first returnable date, such ad-interim orders would be vacated.
If the other side needs time to address the court, the ad-interim measures may continue. If the other side is unable to show any valid prima face case against the ad-interim order, such ad-interim order may be confirmed as an interim order.
I hope I have been able to explain it instead of confusing you more. :)