Many Domain Names in Same URL, What does this mean?

I am completely unfamiliar with domains like these,
For example in Ahrefs, I see http://www.site.differentsite.com/page.asp
Sometimes I even see, site.differentsite.differentsite.com/page.us or something crazy like that. What does this mean exactly?

Those are host names. The domain name is the one near .com.

You can create a whole bunch of these. Even write poetry in DNS.

http://you.can.do.this.and.write.poetry.here.blackhatworld.com/

bartosimpsonio said:

Those are host names. The domain name is the one near .com.

You can create a whole bunch of these. Even write poetry in DNS.

http://you.can.do.this.and.write.poetry.here.blackhatworld.com/

Click to expand...

What is the purpose of doing this in regards to SEO? and how can you do it?

People are doing this because to get brand value, suppose, you can buy a domain like
ebay-com.co-au.in
It seems like they are buying from ebay for newbies, but in reality its not.

xinfiltrate said:

What is the purpose of doing this in regards to SEO? and how can you do it?

Click to expand...

Many years ago the host name really influenced the results. So you could create sony-camera.example.com and buy-viagra.expireddomainhere.com and so on and it'd boost you to the top. Then this got penalized so it no longer works. These days you mostly use it for language selection like wikipedia does it. Some people really do write poetry and shit on their DNS entries, there are DNS easter eggs out there.