Translation:Do not forget your luggage for your trip!
For those who may be confused: my understanding is that pako is the abstract concept of package e.g. "They've got offense, defense, and spirit, the whole package." Whereas pakaĵo is a physical object with the characteristic of packaging e.g. luggage or a package of gum.
I prefer the PIV, which is the entry I went through before posting. You can't rely on translations there.
Of course, I could be totally wrong on this, but here is my reasoning: Remember paki is actually the "natural" root-form. (It is paki and pakaĵo which are fundamenta, not pako). So we "derive" or "backform" pako from a verb (even though the head entries here and on the other dictionaries like yours and lernu's would have you believe the opposite).
So it's similar to the case of manĝi. Manĝo means meal, not food. A meal is an abstract concept, though most people don't think of it that way. We say we get a meal to go, but it is really the food- the manĝaĵo- we are getting packed up. It's a subtle distinction and it can no doubt be thought of differently, but this is what I see at this stage of my learning. Again, I may be wrong, and it may not even be a distinction worth making for most people. If so, please feel free to ignore or correct me with citations.
Yes, anything that is made by packing. For instance, it could be a mail parcel.