If you are not at home at the time of delivery, the package will, if possible, be delivered to one of your neighbours. In some cases, the carrier will attempt to deliver it again on the next working day.
If that also fails, your package is usually sent to a parcel point or parcel locker. You can collect it there on the next working day. You will receive a collection notification or a collection code by email, so keep an eye on your inbox (and possibly your spam folder).
You can also choose to give the carrier permission to leave the package in a safe place. Please note that in this case the sender no longer bears responsibility for the package; this is done entirely at your own risk.