Rakija is a distinctive spirit. Brandy like, in it's concept, a single type of Rakija is made of one type of fruit only.
In terms of Distilling and Bar terminology it a single fruit spirit, fermented and distilled out of either plums, apples, pears, quinces, or any other traditional Rakija making fruits.
As the Arab alchemists developed their methods of distillation, the concept of fruit distillation in order to produce perfume like liquids and different elixirs ass well went do evolve and the spirit production tools and "know how" spread all over Europe.
Serbia and Bosnia, being a part of the Ottoman Empire, at the time, were introduced with distilling art somewhere in the late middle ages up to the 18th century, however the first real market based production of Rakija as a spirit happened in the late 20th century. An Arab word "al rak", meaning "the sweat" made it trough and was accepted all over the region as a synonym for Rakija in general, regardless of weather if it was aged or not, or being produced of any traditional fruit that were common.
Now, Rakija has something original, in its philosophy. The tradition suggests that the it should be consumed as an aperitif, as well as during the meal, or simply enjoyed with traditional o'dourves, snacks and a lokal traditional tapas food. Gradually, the spirit popularity had grown to be a very serious factor in the alcohol industry in the region, as the regional vineyards were affected by Phylloxera. That was the time, when Rakia really made it's name all over Serbia and Bosnia majorly, but in other regions of Southeastern Europe as well.
Being a spirit that is commonly known all around the region, but all of it's types and styles have been distilled and somewhat aged differently, which makes them all subtypes of this distillate.
However, the most popular and the most common is the Plum Rakija, AKA Slivovitza Rakija (Šljivovica).