Pinhole photography is lensless photography wherein a tiny hole replases the lens. Light then passes through the hole and an image is formed in the camera. So, a pinhole camera is a light-tight box with a tiny hole in one end and film or photographic paper in the other.
Its inventor was Sir David Brewster who first took pinhole photographs in the 1850's
To date, pinholes are also used in surveillance and spy cameras and are used in combination with a lens for photographing miniature models, e.g. model trains or architectural models. The pinhole increases the depth of field radically. Some photographers experiment with pinhole enlargers with one pinhole or multiple pinholes. And there are pinhole magnifiers and pinhole glasses.
Here's how to make a pinhole for your DSLR.
Here's an output of a pinhole camera (click on the image for more pinhole images):
[Photo courtesy: photojazz.ws]