This type of printmaking comes under the heading of relief printing. A woodblock or lino cut is made by cutting away areas of wood or lino block with special tools, a little like curved chisels. Ink is rolled over what's left of the original surface and transferred to paper using pressure.
A collagraph can be printed in the same way. However, the surface is built up like a collage by glueing materials onto a cardboard block. Many Artists like the 'rough and ready' feel of collographs, using different textures to experiment and explore how various materials take ink in different ways.
Woodblock, Lino cut, collagraph