Map Art

By placing a large number of blocks players create horizontal pixel art that can be viewed and displayed with maps. 
For a list of map art made on crafters.one see Map Art Archive

Types of Map Art

Mapart is typically distinguished by two criteria, elevation and materials.

Elevation

Stair/Staircase

Every block has one of three shades depending on the height of the highest block directly on its north. If the highest block directly on its north is lower, the light shade is displayed, if it's on the same height the middle shade is displayed (this is the color a block would have on a flat map) and if it's higher the dark shade is displayed.

How Stairs Work in Maps

Flat

Dual Layer

By using a secondary layer above a flat map, you can create a subtle stair effect. This technique is uncommon, but useful in specific circumstances.

Materials

While you can map maps out of thousands of combinations of blocks, due to ease maps are frequently made fully or mostly of carpets. While it is standard to identify carpet maps as such, other categories are not fully defined.
Some possible distinctions on materials
Carpet
Maps made fully or mostly of carpet

Fullblock

Mostly made of blocks other than carpet. Also used to mean "All Blocks" or no restriction on color

Piston Clearable
Refers to a list of materials that are all breakable by pistons. Usually used in conjunction with a machine that breaks the map when it is completed.

Carpet +
Mostly Carpet + any other blocks that may have been used. If a map needs a specific color/s that carpets cant manage, a map maker might choose to use a "fullblock" for just those color/s and carpets for the rest.

Other Categories

Transparent

Maps can have transparency which can lend them a greater degree of interaction with the ingame textures when paired with an Invisible Item Frame. Transparent maps can be map by building a over the void and placing glass blocks at any gap where you desire the transparency to be. 

How to Make Map Art

There are many great resources online for this, and different map makers have their own processes. 
Most map makers use MapartCraft to convert images into schematics.

When you are done with your map make sure to combine it with a pane of glass in a cartography table to lock it.

How to Lock a Map

Then hold it in your hand and do the command /arwydd in the chat to sign it. That signature will transfer to any copies you make and show who built the map.