Q- What is the difference in mirror site and sub domain?

[denniemark]

“You have to be very careful when using Sub Domains because if the content on your sub Domain is too close to the main site, and since search engines look at sub Domains as separate sites, it will degrade your rank because it will consider this as multiple sites with the same content.”
If my site has lots of sub domain, then Google can be banned my site and effect on my site ranking?

[bposervices]

Mirror sites are those sites which are same look wise but url of these sites are different only one person hold all the site which are same in looking. Sub domain sites are such sites which domain are same mean its url same but its appearance is different but their url are not as it is as same.