So check out the Query Shark blog for lots of (mostly bad) examples and an agent's comments. (Not for the faint of heart, but very helpful.)
The diff between querying an editor and agent? Well, think of their different purposes. The editor wants a publishable book. The agent wants a client.
So for an editor, you put the emphasis on your book, what it's about, how long it is, etc. The last paragraph might be about you, but most is about the book. Generally, that's what the editor is going to be dealing with. Not your career, no matter what they might say at conferences. Editors work for their publisher's success, not yours. That doesn't mean they don't care about you and your career, but the book and how it's going to help make money for the publisher, or fill an open slot in the schedule, or win a prestigious award and result in good press for the publisher, that's what really matters.
In the agent query, you want to talk about the book you're submitting, but the agent is also going to be interested in you as a writer. What else are you writing? What genre or sub-genre do you mostly concentrate in? What is your background and how is it relevant to your writing career? (Like you live in a fishing village in Oregon, and that's where you set your books. Or you work in the oil industry and write "oil thrillers" -- don't laugh, there is such a thing. In fact, I think some writer invented the BP oil spill before it happened. I recently saw a book -- I'm fuzzy on details-- where the main character tutored rich kids in how to write college application essays and got dragged into the corruption of writing them herself... well, turns out the author had done that, and I'm sure she explained that in the query, as it's all over the marketing material that's out now.)
Don't get too high-flown here when you talk about your future plans. Your life coach might want to hear about your expectations of a quick rise to the top five of the NYT list, but the agent just wants to hear that you intend to write a four-book series in this universe and then have a YA version with the same basic storylines, and then you intend to parlay that success into a follow-up series about.... (You're not actually swearing you'll write all those.
So in an agent letter, you might do the first paragraph or two about the book, and the next about you and your background, and then one or two about future books and future plans.
Just a different focus. See what I mean?