What is the difference between native and denaturing gel electrophoresis?

In native gel electrophoresis, the RNA or protein of interest is maintained in its normal or native structure while running it through the gel.

In denaturing gel electrophoresis, a reducing agent is added to the sample, gel, or buffer before or during gel electrophoresis. The reducing agent separates the bonds within the RNA or protein molecule, reducing the RNA or protein molecule into its most linear structure.