Pǔxī (literally 'west of the river Huangpu'), is the historic area of Shanghai, to the west of the river Huangpu that bisects the city. While the area on the other side of the river, Pǔdōng (literally 'east of the river Huangpu') is expanding rapidly as Shanghai continues to develop, Puxi remains Shanghai's cultural, residential and commercial centre.
For more information, see the Wikipedia article on Puxi.