India was one of the first places where human beings came to after they left Africa, travelling along the coast around the Arabian Peninsula and the Persian Gulf. The first people probably arrived in India about 50,000 BC.
By about 3000 BC, the Harappan people were building Bronze Age cities along the Indus River (in modern Pakistan). These cities traded with West Asian cities. But soon after 2000 BC, the Harappan cities collapsed - nobody really knows why.
Not long after the collapse of the Harappans, some Indo-European people came south from Central Asia to India, bringing with them horses, chariots, and their language. The newcomers' religion mixed with the local religion to form Hinduism, and we call their culture Vedic. The caste system got started around this time. Around 800 BC, these Vedic people moved from the Indus Valley to conquer all of North India, including the Ganges valley.
By 539 BC, the Persians under their king Cyrus the Great were attacking northern India (modern Pakistan) and making some of it part of the world's first empire. Alexander, when he conquered the Persian Empire in 323 BC, also attacked northern India.
But already Indian kings were forming their own empires. The first was the Mauryan Empire in 321 BC. The Mauryan Empire collapsed in 184 BC, and there was a period of small kingdoms, but then in 320 AD the Guptan kings formed another empire which lasted until 550 AD. Other large kingdoms formed in southern India as well.
Beginning in the 400s AD, however, waves of Central Asian and West Asian people began to invade India from the north. First the Huns attacked, then after the Guptan Empire collapsed Muslim invaders took over northern India and established the Delhi Sultanate. Finally the Mongols made repeated attacks on India in the 1200s and 1300s AD. These attacks were limited to northern India, and in the south, the Indian kingdoms continued pretty much undisturbed.
To find out more about Indian history, check out these books from your local library or from Amazon:
Eyewitness India, by Manini Chatterjee (2002). Written for kids.
Ancient India, by Virginia Schomp (2005). Written for middle schoolers. Very good for reports.