The nozzle is the component of a 3D printer that deposits the melted material into the platform. Usually, it’s made up fo brass and a 0.4 mm diameter, which is a pretty standard measure.
There are nozzles made of other materials, such as steel or hardening steel. However, brass nozzles are the most common ones.
It can come in different shapes and dimensions, starting from 0.25mm up to 1mm diameter nozzle.
The smaller the nozzle, the better the quality of the print is, and the less you see the layers.
The side effect is that the smaller the nozzle is, the slower the 3D printer works. This is the reason why we print small objects with small nozzles.
Another bad note is that 0.25/ 0.3 nozzles get clogged easily because of small particles inside the filament, for example with carbon-added elements or wood-added fibers.
This doesn’t mean you can’t print the materials above, it’s just that it won’t be so simple.
Large extruders such as 0.8mm cut significantly the printing time, but they leave a poor surface finishing and the dimensional precision gets a little bit compromised.