Wang is most often the Mandarin form of 王, whose ordinary meaning is "king" or "royal." Multiple Chinese lineages adopted 王 to mark remembered royal or noble status; Korean Wang (왕) uses the same character. That character gloss is agreed; it does not mean every Wang descends from one emperor.
DAFN also lists Mandarin 汪 (a different character) and other streams under the romanization Wang. Cantonese Wong is often the same 王. Like Kim, this is a clan surname filed under nickname for the character's sense among the product's four types.