Doxxing and DDOSing are two separate things. Doxxing is exposing someone's personal information, such as home address, phone number, etc., often with the intent of targeted harassment against that person.

DDOS, which stands for distributed denial of service, is typically used, as you said, to bring down a website or other online service by flooding the server(s) with traffic until it cannot respond to any in a timely fashion, making the service inaccessible.