Who found it first. Is it romans? Did romans used them in real battles? If the Romans used it in battles what kind of strategy they operate?
The chariot, a lightweight spoked-wheel vehicle for passengers, first appears in the Eurasian steppe, to the north of the Aral Sea. Specifically, the earliest chariots ever found are associated with the Sintasha culture, in an area spanning the Russian-Kazakh border, and are dated to about 2,000BC. This is about 1,500 years after the earliest known wheeled vehicles and the domestication of the horse. The wheel and the domestication of the horse were independent - the oldest wheeled vehicles known are ox-drawn wagons from the Ukrainian steppe and human-powered mine carts from the Balkans. The development of the spoken wheel (earlier wheels were solid wood) allowed lightweight chariots to be made, and when horse-drawn, were the fastest wheeled vehicles the world had known.
The chariot was used in war. It appears to have been primarily used as an archery platform, and was, at least some few centuries after the earliest chariots, accompanied by the horn-and-sinew reflex-recurve composite bow (the Sintashi culture knew archery, as indicated by arrowheads and parts of bows, but no complete bows have been found). Artwork of chariots in war and hunting usually shows archery:
Late chariotry was less archery dependent. The Achaemenid Persians used "scythed" chariots - chariots with blades attached to the wheels, and the British used chariots for (a) javelin throwing, and for (b) rapidly-deployable infantry. As described by Julius Caesar:
In chariot fighting the Britons begin by driving all over the field hurling javelins, and generally the terror inspired by the horses and the noise of the wheels are sufficient to throw their opponents' ranks into disorder. Then, after making their way between the squadrons of their own cavalry, they jump down from the chariot and engage on foot. In the meantime their charioteers retire a short distance from the battle and place the chariots in such a position that their masters, if hard pressed by numbers, have an easy means of retreat to their own lines. Thus they combine the mobility of cavalry with the staying power of infantry;
The Iliad described chariots largely as battle-taxis: great heroes can ride to the battlefield in style, and then dismount to fight.
It's possible that the chariot enabled the Indo-European expansion, which was begun by the successor cultures to Sintasha culture. This expansion took Indo-European languages and the chariot (and possibly the composite bow) east to China, south to Iran and India, and west into Europe. 500 years after its development, the chariot was used in China, in India, in the Near East, and in Europe. Egypt adopted the chariot - their first significant use of the wheel - after being conquered by chariot-users.
At about this time (1500BC), horses were being ridden, but there is no evidence of the military use of horses for cavalry. Early in the 1st millennium BC, cavalry were being used in battle, and the chariot lost its exclusive possession of speed on the battlefield. Still, the chariot persisted for another 500 years on the Persian battlefield, and was used even later in Britain. As the chariot faded from the battlefield, they remained in use as ceremonial vehicles, and for racing, and their descendants are still used in racing today:
Did romans used them in real battles?
The Romans no longer used chariots in battle when they began their conquests. The major known case of the Romans facing chariotry was in Britain, as described above.
The second-last major user of the chariot appears to have been the Chinese, who used them in battle in the late 1st millennium BC. They had been obsolete as major weapons on the battlefield for 4-500 years by that time, but were still used as command vehicles by officers, and some specialised chariots were sometimes used for fighting.
The third-last major user appears to have been the Persians, against Alexander the Great's invasion. As in China, the chariot had long ceased to be a major weapon, and appeared in small numbers in the form of the scythed chariot.
