Let's say you have a lot of toys and you want to share them with your friends. You could just give them all the toys, but that might take a lot of time and it could get messy. So instead, you decide to put all the toys in a big toy chest and have your friends come and take out the toys they want.
Now imagine instead of toys, you have a lot of information that you want to share with a lot of people. That's where a scalable network application package comes in. Instead of giving each person all the information at once, it puts the information into a big container (like the toy chest) and allows lots of people to access it at once.
But what makes it "scalable" is that if you have more people trying to access the information, the container (or "network") can get bigger to hold more information and allow more people to access it without slowing down or crashing. Just like if you had more friends who wanted toys, you could get a bigger toy chest to hold more toys and make sure everyone can get what they want without any problems.
So a scalable network application package is like a big container that holds lots of information and allows lots of people to access it at once, without any problems even if there are a lot of people using it.