Several programs and plugins make use of schematic (.schematic) files. Popular uses include WorldEdit and MCEdit. Schematic files allow you to export blocks for pasting or importing to a different world on your local client or on a server.
EXPORTING / CREATING A SCHEMATIC:
To create a schematic (with WorldEdit), select a region with the wand (//wand) and copy the selection to your clipboard (//copy). After you've done that, you can save the selection that is copied to your clipboard by typing //schem save nameofschematic. WorldEdit will then save the selection to /plugins/WorldEdit/schematics/nameofschematic.schematic.
IMPORTING / LOADING A SCHEMATIC:
To load a schematic (with WorldEdit), drop the schematic file that you exported into /plugins/WorldEdit/schematics (if the folder does not exist, you can create it). After, load the schematic to your clipboard by typing //schem load nameofschematic. WorldEdit will load the schematic from file, and then prompt you to paste it like you would with a normal copy and paste operation.
Important Note: If your schematic consists of over 1 million blocks, we highly recommend that you utilise a plugin like AsyncWorldEdit in order to prevent interruptions or crashes. WorldEdit by itself is very inefficient when it comes to pasting and loading large schematics without crashing the server, and this plugin fixes that issue.
MCEdit also makes use of the schematic file format. To create a schematic, select an area with your mouse, and then hit the 'Export' option when the menu pops up. After you've done that, you can use the import steps above to paste it in.