YSK Yelp replaces restaurant phone numbers with a special number that charges that business a marketing fee. If you find a good restaurant on Yelp Google their phone number instead so they don't lose any money.
from /r/YouShouldKnow
YSK Yelp用一个特殊的号码代替餐厅的电话号码，向该企业收取营销费。如果你在Yelp上找到一家好的餐厅，可以用谷歌搜索他们的电话号码，这样他们就不会损失任何钱。