You already got a mosaic design, either by an artist or by yourself.
Before submit your order, double check the mosaic design and make sure you like it.
Purchase a complete mosaic from a merchant.
Submit your order, a merchant agent will contact you to discuss order details, include price, delivery day, package etc.
Then the merchant will build your mosaic in their workshop, split it into multi small sheets, package them, and delivery to you.
Purchase a raw tile package mosaic from a merchant.
For some reason you want to build the mosaic yourself.
Submit a tile package order, merchant will not assemble the mosaic. they will count and put tiles into individual bags, then package them, and delivery to you.
With tiles you will receive tools, glue, grid pallet, and other accessories, use them to make your own mosaic.