An "incomplete summary" (or "partial summary") with a possible negative tone ("Kind of" means "incompletely" and "sums things up" means "summarizes [the topic at hand]"); to me, there seems to be a dissatisfied tone implied by the comment (that the summary is incomplete) that is also bundled with an expectation that the summary could have (or should have) been better somehow.
Regarding popularity, this isn't a phrase that I recall hearing or reading anywhere (although it's not entirely unfamiliar), so I don't consider it to be popular (I'm in Western Canada; there may be other places where this phrase enjoys frequent usage).
Dream board is indeed a new term (also called a Vision board). That's why the author put it in quotes, to warn readers that they might need to figure out exactly what it meant. But the words are pretty transparent - it's just a creative, inspiring picture/text "collage" of all the things that are important to you now, and more particularly your aspirations for the future.
I assume the principle is that by creating one you're forced to think consciously and coherently about your "life plan". And once you've got it, you can keep looking at it to remind yourself what you want and how you're supposed to get it. One-on-one lifestyle coaches/personal trainers have routinely incorporated the technique into their work, but I don't think either of those two terms were normally used (if at all) until a few years ago.
It looks like a rapidly-growing internet phenomenon that in many cases is really just scamming - in most cases you won't be getting any personalised guidance at all. I haven't looked in any depth, but from a brief scan there are plenty of people trying to make money out of persuading others that this sort of thing will turn their unsatisfying lives around.
Most people's lives are no more likely to be turned around by getting involved in "dream boarding" than by buying a lottery ticket - you're usually being sold the chance to dream, not something that will actually realise your dream. IMHO in a few years time it'll be looked on much as we currently see pyramid selling. A few get lucky - but most will be at best disappointed, at worst exploited.
At the linguistic level (this is ELU, after all) I would guess that dream board is somehow more appealing to gullible people. Vision boards don't have quite the same sense of fairies waving magic wands and giving you your heart's desire. Competent qualified therapists would probably call them Mind Maps or Goal Maps, and draw on a wealth of skills to help you create one if they thought it would be effective in your particular case.
Best Answer
It doesn’t really mean anything by itself, it’s being used for rhetorical effect in juxtaposition with “sat back and let things happen to them.” This is emphasised by the slightly nonsensical idea of people happening (rather than events or abstract ideas).
The implied sense of the whole paragraph is that people of accomplishment are active, making things happen, rather than passive, waiting for things to happen.