The principles behind the technology are very simple, but actually implementing it in a way that is secure, decentralized, and robust is incredibly difficult and requires a great deal of technical sophistication. Since a lot of this stuff is some what new, people take liberties to create jargon for describing it. It's not that unreasonable, when people come up with something they like to name it and sometimes those names can be fancy or unfamiliar.
The main problem is that running programs on Ethereum is expensive, every computation costs money. Past efforts to create a fully automated stock market on Ethereum ran into these costly problems and the end result is that the exchange ends up having very little liquidity or users. Imagine a version of eBay were just placing a bid costs you money. Well with a market you place bids and cancel them, and often time do that repeatedly as you gain new information. If every single one of these actions costs you money and you need to wait potentially 20-30 seconds for your action to be confirmed by Ethereum (think of Ethereum as a very very slow computer), well people become hesitant to participate.
0x is a system to remove the vast majority of an exchange's function off Ethereum and only use Ethereum as a settlement layer or to resolve potential disputes. To do this, they introduce a market maker system where market makers act as middle men between people adding liquidity and people removing liquidity. These market markets do not use Ethereum to act so a user can interact with them without worrying about fees or time delays. To be a market marker, you need to put up some collateral into a pool, if you perform your function correctly then you get rewarded with fees, if you make a mistake or try to screw someone over, you lose your collateral.
The market maker system 0x uses is what allows basically 99% of activity to operate outside of Ethereum and drastically reduce costs and improve performance. If everyone acts honestly then things run smooth and cheap. If someone decides to do something funny, then and only then does the power of the Ethereum blockchain get involved and a dispute resolution process is engaged, there is a cryptographic system to verify which participant is at fault and that participant gets penalized.
That's all 0x is in a nutshell, it's a system that markets can participate in to run cheap and fast decentralized exchanges.
Okay so now the question is... who runs 0x itself? Who makes decisions about 0x, its future, how will the exchange improve over time?
This announcement is an answer to that question. Instead of 0x itself being a centralized entity, 0x is creating a set of computer programs that will run on Ethereum where future upgrades are voted on by people who own 0x tokens (ZRX). Someone can propose an upgrade to the system (by uploading an Ethereum program to the Ethereum blockchain), people who own 0x tokens can vote on the proposal. If the proposal gets the necessary votes, then the proposed program will receive write permissions to resources associated with the 0x system.
One of the resources the program will get write access to is a pool of 0x tokens. Initially there are 2 million 0x tokens that will be placed in a pool, and proposals can make use of those tokens to fund activities or do who knows what, it's basically some seed-financing to get the ball rolling.