In case your flight has been cancelled, you may be offered an alternative flight (re-routing or schedule change), or in some cases a full refund. However, if the cancellation has been caused by a critical financial situation (insolvency, bankruptcy, etc.) no alternative flight or immediate refund can be offered.
If your booking is impacted by a delay, you may be entitled to compensation from the airline, depending on the delayed time and the distance between the origin and the destination.