Buckwheat is also known as common buckwheat, Japanese buckwheat or silver hull buckwheat. Buckwheat seeds come from the species Fagopyrum esculentum.
To get maximum flavour and give Buckwheat seeds a longer shelf life, they are usually toasted until they turn brown in colour.
The toasted seeds (Groats) have a more assertive and toasty flavour. They are referred to as whole toasted buckwheat groats or simply referred to as Kasha.
The whole toasted groats can also be ground into flour or cracked into coarse, medium or fine granules.
Here are the buckwheat Seeds (Groats) before they are toasted
Point to Note
Buckwheat flour and groats must be used fresh because their fat content is high and they soon become rancid. (Alternative Field Crops Manual)
Here are Buckwheat Seeds after they are Roasted