Is this bad?

Hi there

I recently just realized that some new pages appeared on my website when using a command "site:mydomain.com" , the pages made a new "category" (as i might call it)called "/tag/" and made some duplicated posts with meta tags, the only difference is the link that contains the meta tags.What the hell happened here?
The plugin i was using recently was this one:
http://wordpress.org/plugins/strictly-autotags/
But i didn't saw anything related to this.
I hope you understanded what happened.

Best
Dikkill

Its normal..Dont worry about it..This will not affect your site/seo

If you tag anything in your posts, it creates this automatically. Its basically another way for people to search through your site, like categories. Since your using the plugin, it's been doing this for you. It actually helps SEO as it creates better traffic flow.