This is a cumulative update, using Microsoft's newer strategy of adding new features but not necessarily turning them on. This gives them more control in case problems, e.g. with certain hardware, become apparent, and lets them slow walk introduction of new stuff if/when they feel it's necessary. Today the update is available in the Insider Beta and Preview channels, while a slightly older version [that *should* update to current] is available to Insiders as an ISO.
I'm writing about it because I want to urge a bit of caution. Hopefully it's nothing to worry about & is just me or this one copy or... but I have a copy installed on this PC, which is Very mainstream as far as components go, and it Has Not Been Good. Put it this way... if I boot into that Insider copy and do whatever, try an app or update Win10 etc., if I get out of it [restart the PC] without Win10 crashing, I consider it a notable success. Right now it's about 50/50. I've never had a copy of WIn10 behave so badly before.