What is elution ?

During gel electrophoresis ,the separated DNA fragments can be visualised only after staining the DNA with a compound known as ethidium bromide followed by exposure to UV radiation (you cannot see pure DNA fragments in the visible light and without staining).

You can see bright orange coloured bands of DNA in a ethidium bromide stained gel exposed to UV light . The separated bands of DNA are cut out from the agarose gel and extracted from the gel piece. This step is known as elution.