With photolithography, what most chips are made with, the resist is developed by exposing it to UV light. A mask is used so that the desired parts of the resist are left behind, and the rest is washed away. Contact photolithography places the mask directly against the silicon wafer because it helps the optics during exposure, but the mask doesn't directly remove the resist.

In nanoimprint lithograhy, a stamp is pressed into the resist on wafer and leaves the desired pattern behind.

The difference is that the resist is removed mechanically instead of chemically.