If you are not at home at the time of delivery, the package will, if possible, be delivered to one of your neighbors. In some cases, the carrier will attempt delivery again on the next business day.
If that also fails, your package is usually sent to a parcel point or parcel locker. You can pick it up there on the next business day. You will receive a pickup notification or a pickup 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 takes responsibility for the package; this happens entirely at your own risk.