This collection includes all plants known to fix nitrogen into the soil. Some of these plants are more efficient than others, some produce a crop too, some are native and some are not native.
What is a 'Nitrogen Fixer'?
In short, nitrogen fixers are sort of like plants that fertilize as they grow, which helps limit/eliminate the need to add nitrogen to your orchard. Nitrogen inputs (eg. urea) are one of the most common fertilizers used in conventional orchards.
Nitrogen fixing plants have a special relationship with nitrogen floating around in the air, and can transform it to a digestible for for plants and hold (or 'fix') it into the soil so the plants can then up-take it through its roots. This link further explains the process.