Bulgur (also spelled "bulghur") is cracked wheat grains. When a recipe says bulgur I use Couscous as it is easier for me to buy.
Couscous is millet flour, fine semolina, or crushed wheat - belongs to pasta family.
Both used the same way.
You can buy bulgur wheat from most supermarkets. It's down by the lentils and pearl barley type stuff. I love it. It's got a better texture than couscous I think? Stands up really well to fresh fruit in a salad. Pomegranate seeds, apple, citrus etc and also it makes the most delicious porridge!! Cooks slower than oats but worth the wait.