What is the difference between "gluten-free" and "very low gluten content"?

What is the difference between "gluten-free" and "very low gluten content"?

According to the Codex Alimentarius Commission and EU Directive of 20 January 2009, food products containing no more than 20 ppm (2 mg/100 g) of gluten are "gluten-free". Food products with 21–100 ppm must be labelled with "very low gluten content".