Xīnběi 新北 (generally known as New Taipei in English) is an administrative division of Taiwan 台灣 surrounding Taipei 台北. Technically it is the mosts populous city in Taiwan but that's mainly because it includes much of Taipei's urban sprawl. There isn't any sort of unified identity to New Taipei; it's merely an administrative contrivance.
That being said, New Taipei is home to some of the coolest stuff within easy reach of the big city. The attractions are far too numerous to list and start with historic Tamsui 淡水, the hot springs of Wūlái 烏來, the twin mining towns of Jiǔfèn 九份 and Jīnguāshí 金瓜石, Fulong Beach and the Old Caoling Tunnel in Gòngliáo 貢寮, Yeliu Geopark and the UFO village in Wànlǐ 萬里, and the entire Píngxī 平溪 railway corridor, among others.