Hey @poseid, happy to help!
Our development kits (the Core, the Photon, and the Electron) are tools designed for people building hardware connected to the internet; the Core and Photon use Wi-Fi and the Electron uses a cellular connection (2G/3G).
These are internet-connected microcontroller development boards, and so far we’ve used STM32 MCUs (ARM Cortex M3), though that may not always be true for future boards. The boards are inexpensive and very powerful (when compared to 8-bit processors like an Arduino Uno).
Because the boards are designed solely for devices that are connected to the internet, our development experience also relies on that internet connection. Although you can program them over USB, our tools are designed around over-the-air firmware updates. You can write firmware in our web IDE, Particle Build, or in our downloadable IDE, Particle Dev, which is based on Github’s Atom project. You can also use our Command Line Interface to push software that you’ve written in another IDE (many people use other IDEs like Netbeans or Eclipse).
Our development boards come with a cloud-based messaging platform that lets you easily send messages to- and from- the devices in a secure way regardless of where you are. That platform is included for free.
Our platform is particularly well-suited for people who are developing products which they want to scale. If you’re building a prototype and down the road you want to make 10,000 or more, we sell hardware inexpensively at volume or we can pass you off to our semiconductor partners to get it even cheaper. We also sell our cloud platform to companies deploying IoT products, and it’s currently being used by hundreds of companies, from Fortune 500 OEMs to tiny start-ups.
When it comes to Arduino, we use Wiring, the same programming framework as Arduino, which we have ported to the STM32 microcontroller. Because of that, many Arduino libraries work out of the box on Particle, although some require porting (since our hardware is a different architecture). There are hundreds of libraries that have already been ported to Particle by the community, and those can be accessed through Build, our web IDE.
That said, Particle is not a completely Arduino-compatible product; you can’t (yet) use the Arduino IDE, and our products have a different footprint. Our original Kickstarter campaign for the Spark Core did call it “Arduino Compatible”, but that’s a confusing way to describe it, because “Arduino Compatible” means different things to different people. Since then we now communicate our development experience as “Arduino-like”. If you’re familiar with Arduino, it’s very easy to transition to Particle, but it is a different experience with different tools that are specifically designed for internet connectivity.
Over time we’d like to increase our compatibility and portability with the Arduino ecosystem, and we’re working on making our libraries work with the Arduino library spec (which didn’t exist when we launched). But for today, the best way to describe Particle is “similar to Arduino but different, and specifically designed for developing internet-connected hardware”.
Hope that helps!