Plagiarism: the unauthorized use or close imitation of the language and thoughts of another author and the representation of them as one's own original work. (Dictionary.com Unabridged. Based on the Random House Dictionary, © Random House, Inc. 2009.)
Notice how I gave credit to the definition above? Notice that I provided a source AND a link? Notice how even dictionary.com provided their source?
This is what you do when you copy stuff from any source and use it for your own purposes, whether from a printed book or posted on the Internet.
When you copy the wording from one blog (example: MINE) and post it straight on another blog (example: YOURS), and you give no source, that is called plagiarism. It's illegal, unethical, and extremely bad manners.
Folks, I have StatCounter (see bottom right sidebar). About once a month, I check out who my visitors are and where they're coming from. When I see a new referring blog, I go visit it. All too often (once is too often, and it's happened way more than once), I find blogs by writers, on the subject of writing, that have lifted my posts and put them on their blogs—verbatim! Without credit back to me. (Shame on you!)
And when I say verbatim, I don't mean that they saw that I talked about POV on Monday and they did their own post on POV on Tuesday, pretty much making the same points I did but putting it into their own words (although that's irritating to me and just kind of lazy on their part). No, I literally mean "verbatim"—as in, "in exactly the same words; word for word."* (Notice how I did this quote differently, but still gave credit to the original source?)
As a writer, you should know better and do better. If you don't know better, inform yourself. And quite stealing my stuff!
P.S. As a publisher, yes, I researched authors who submitted to me and read their blogs and websites. If I discovered that they used someone else's words on their sites without credit, they were rejected outright and were added to my "never publish this person's work" list.