adservice.google.co.kr - Domain Info
The following page provides details on the application and list of hostnames associated with the adservice.google.co.kr domain. The list of notable hostnames that were detected come from not only DNS requests, but also HTTP headers, TLS certificates, DNS hinting, and other deep packet inspection methods.
You can access the full data set via the Netify Data Feed API.
Though Google is the world's most used search engine, most if its revenues come from advertising products and services. Google Advertising is a catchall for the various marketing platforms from Google.