
google.com is a large domain for all Google services, Google created subdomains for product and services segmentation
a. play.google.com - a subdomain to handle mobile apps and ebook content.
b. adwords.google.com - a subdomain to handle advertisers biding and keywords
c. drive.google.com - a subdomain to store cloud content and document
d. support.google.com - a subdomain to manage user question and product support
e. plus.google.com - a subdomain to handle social media contents
yahoo.com is a large domain for all Yahoo services, Yahoo created subdomains to manage multi region content.
a. hk.yahoo.com - a subdomain to handle Hong Kong local contents
b. malaysia.yahoo.com - a subdomain to handle Malaysia region contents
c. sg.yahoo.com - a subdomain to handle Singapore local contents
d. uk.yahoo.com - a subdomain to handle UK region contents
e. ca.yahoo.com - a subdomain to handle Canada local contents
The benefit of subdomains
- unlimited subdomain, a large domain can create as many subdomain as needed
- save cost, there is no additional fee to create subdomains
- assign different IP for each subdomain. Therefore it is not necessary to host all content in the same server.