What does "PREORDER" mean?

What Does "PREORDER" mean when it appears in the item title?

Preorders are inventory that has already been ordered and are on their way to Bethany's Jewelry Jam stock!

Add these items to your cart and check out as usual; they will automatically ship when they arrive into stock!

NOTE: Orders ship complete! In other words, your order will wait to ship until all items you've ordered have arrived.