A swap is where you sign-up for a specific category in a group, you make a set of your category for each person in that group, and mail it to the hostess. She will then sort everything for each person and will then mail you back a complete set for that group.
So, let's say you sign-up for the following group in a Magic Kingdom Swap"
A. Rides
1. It's a Small World - Tinkerbell
2. Peter Pan's Flight - AWM
3. Dumbo - NemoMom
4. Winnie the Pooh Ride - MorgansMom
5. Snow White's Scary Adventures - Party of 3
Okay, you signed up for It's a Small World, so you will make 5 sets for that group. Your set would contain however many elements the hostess specifies. Let's say this one is 2 elements. You choose to make a topper, a photo mat and a journal box. That is considered a set.
You've made your 5 sets for It's a Small World. Now, you will mail all 5 sets to the hostess.
Everyone else made 5 sets for their ride too.
The hostess gets all the sets and sorts them out so that each person gets one of everything.
The hostess mails back to you and when you receive your package, you will have one set for each of those 5 rides.
Does that help clear it up for you? Let us know if you have questions.