The best way to get to know Linux is to install it and use it. Go to
www.distrowatch.com, pick one of the
major distributions that sounds interesting, install it, and use it. No one here is going to hand-hold you through the entire process. Rather, you should come back and ask questions if you get into trouble.
You say you want to get a certification? You won't be successful in that endeavor unless you learn how to find things out and progress on your own, without someone spoon feeding you everything. Personally, I'd never hire an admin or developer that can't think and learn for themselves, regardless of what pieces of paper they have (I'm one of those folks who's extremely skeptical of certs in general, though they have their place).
In terms of videos, go to YouTube and search for "introduction for Linux" and the like. Do you really mean to imply that you're a Windows expert, but can't figure out how to use a search engine? Sorry if this sounds a bit harsh, but you have to put some minimal quantum of effort into learning anything, and Linux is no different.
A couple more helpful links:
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http://rute.2038bug.com/index.html.gz
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http://www.catb.org/esr/faqs/smart-questions.html
