Gel electrophoresis is a method used to separate biomolecules like DNA and proteins based on size and charge. It involves placing the molecules in an agarose or polyacrylamide gel and applying an electric current, causing the molecules to migrate through the gel at different rates depending on their size and shape. Agarose gels are used to separate larger DNA fragments while polyacrylamide gels separate smaller proteins by inducing a linear structure and negative charge using SDS detergent. Gel electrophoresis has applications in forensics, molecular biology, genetics and other fields.