Models are constructions made by the community to add characters, decorations and many other useful things.
Press "N" when you're in a project. You can choose a small, medium or big model format. You can build a model with the maximum size of 24x24x24 blocks.
First enter a project, you can open your inventory and place any model, no matter if it's a self made one or a purchased one. You can edit them by pressing the right mouse button and clicking on the "Edit model" button.
You can sell your models in the store by pressing "i" in the bottom right-hand corner of the model, go to the "i-con info" option, where you need to give your model a name and description. If you have done that. you can sell it. Your model will now appear in your shop for sale. You can buy other's models for 10 Gold.