I'd love to hear some opinions here on the difference between "angel" and "seed" funding. From some information I've gathered by reading and talking to people,

I'd love to hear some opinions here on the difference between "angel" and "seed" funding. From some information I've gathered by reading and talking to people, "seed" funding is for product development, right? You might have a prototype, but you really haven't been able to prove product/market fit yet for lack of funds? In that case it seems that some "seed rounds" (eg. Lanyrd and OnSwipe) are really large. I also gather than the size of the investment is not what determines the "stage" of the round - ie. Tech Crunch reported $1mil in "seed funding" for OnSwipe. They later went on to raise a "Series Awesome" of some $5mil. Then there's "angel investment" which seems to be much less formal and probably more likely in the tens of thousands than hundreds of thousands (or $1mil+). What I'm really wondering is: at what stage are these companies with their products when they get these seemingly enormous seed rounds? A lot of what I read about "getting investment" seems to suggest you need traction, paying customers, product/market fit, a track record of running successful companies, etc. But then it seems to me (from the outside, at least) that some companies manage to get quite a substantial investment as a "seed round" which seems to be (again, from the outside I really have no idea what's going on under the hood here) largely to finish off an otherwise prototypical product so that it can be released to the target market. It's my understanding that once you get to "Series A" you're basically not a "startup" any more (by the definition that a "startup" exists to find a business model). As you may be able to tell, I'm thoroughly confused. Any advice or links to relevant articles most appreciated.