Lepinja bread, also called lepinje or somun, specifically, in Bosnia and Herzegovina, is indeed the daily bread of the Balkans. It contains baker's yeast but also baking soda (or baking powder) which is supposed to aerate it and give it a lighter side. It is also known as lepinje za cevapi (flat bread for cevapi) because it is most often served with cevapi (mititei) sausages - grilled ground meat rolls with the raw ground onion folded inside.
It is baked in the oven. And, just like the pita, two layers separate during baking and its hollow centre forms a pocket. You can open it on one side and fill it to make a sandwich or cut it in half or even in four to make smaller sandwiches.
If the lepinja is baked in the oven, there are also two other kinds of breads baked in the Balkans, the mekike or skoro pa dijeltane, which are baked in a pan or on a hot stone. The lepinja has no specific origin. Its history is simply that of the bread. The word bread comes from the Latin panis which itself is divided into two parts, pa meaning "long" and nis meaning "to feed".