A nanopore is a very small hole
A nanopore is a nano-scale hole. In its devices, Oxford Nanopore passes an ionic current through nanopores and measures the changes in current as biological molecules pass through the nanopore or near it. The information about the change in current can be used to identify that molecule.
Holes can be created by proteins puncturing membranes (biological nanopores) or in solid materials (solid-state nanopores).