Budo actually means martial arts of Japanese origin, whose primary goal is the spiritual, ethical and moral evolution of the individual.
Words "Bu" and "Do" can be respectively translated to "martial way", but they do have several secondary meanings. We can describe Budo as a concept whose principle is to control violence and achieve self-realization. Budo does not have an external enemy, only an enemy within, the ego, which must be fought. It seeks to unite body and mind in order to allow the body to act freely and intuitively without fear, emotions or concerns.
"Do" is the Japanese translation of the Chinese term "Tao". If in China Tao has been seen in a more religious way (as the path of the Universe), in Japan it was interpreted into a more practical sense, by the training of various forms of arts in order to test his validity and to guide human relations.
It is necessary to know the japanese historical context to understand how Budo association with martial arts evolved.
Between the 8th to 16th centuries, several wars occurred between clans of warriors. What prevailed at this time was the Bujutsu (science or techniques of war) represented by a set of martial arts (with bare hands or with weapons) which could be trained only by bushi (warriors) to be used in battle. Ethical ideals such as obedience, loyalty and respect existed in Bushido (a code of conduct for the bushi).
From 1603 to 1868, Japan experienced a period of peace and unity (known as Edo period) under the dictatorship of the Tokugawa shogunate. The bushi had their functions oriented to more bureaucratic or artistic activities (poetry, theater, tea ceremony). Consequently, the Bujutsu had to re-adapt to these new times. Budo was assimilated and the martial arts began to be designed to serve the individual and society as a whole (this can be seen as the classical Budo). The different schools of martial arts became open to the public.
In 1868, the Meiji era began with the abolition of the Shogunate, and the warrior class ceased to exist. This led to the rise of the so-called modern Budo (Budo Shin), which gave emphasis to ethical, moral and spiritual development of the individual. To preserve the spirit of the warrior, hard discipline in training was enhanced.
Jigoro Kano saw the educational value of Budo and incorporated it into the creation of Judo (based from Jujutsu). Other fighting systems soon followed the same path: Aikido (inspired from Aikijutsu), Karate-do, Kendo and many others.