In size, Punjab is Pakistan’s second largest province, after Balochistan, and the most densely populated. The name Punjab means “five waters,” or “five rivers,” and signifies the land drained by the Jhelum, Chenab, Ravi, Beas, and Sutlej rivers, which are tributaries of the Indus River.
Urban civilization existed in the Indus River valley from about 2500 to 1500 BC, when, it is believed, Aryan incursions brought it to an end. The area entered recorded history with the annexation of Punjab and Sindh to the Persian Empire by Darius I (c. 518 BC). The founder of the Maurya dynasty, Candra Gupta, incorporated the region into his Indian empire about 322 BC. The first Muslims to penetrate northern India were the Arabs, who in AD 712 conquered the lower Punjab. The rest of the Punjab was conquered (1007-27) by Mahmud of Ghazna.
Punjab is connected by road or railway to India, China, and Afghanistan, and its major cities are linked by road.
(taken from punjabi.net)