Seller Logic | Ready Stock And Pre Order Terms

Assalamualaikum wbt.
Hello fellas, have you heard of this term before? Maybe you’ve heard it somwhere, but mostly when people selling products this term will be use so much.
Are you know what this term refers to? Or you dont care and dont want to know? In that case well you do not need to read further because today I’m just gonna write what does this two things really meant.
1. Ready stock
Ready stock item means, items already in stock, once a buyer make payment for it, seller will pack and send to the buyer. The only gap between seller and the item is delivery (gonna be with postage, pick up or COD).

2. Pre Order Items. 
A payment/deposit must be done before the due date given. Only after the date that the item gonna be made.

For example, Mak Non open pre order for her Mak Non’s Tart Nenas. At this time, the tart does not prepared yet, after receiving payment/deposit (or she decide to put due date and collect several other orders) then the tart will be prepare based on the order list. So after an amount of time only then you’ll receive the tart in your hand. 
May that clear your understanding regarding these two terms. 
Till then, ^^