Particular is a plug-in from a third party developer. If you want to try it out there's a demo mode. If you need it, you have to pay for it. There are lots of 3rd party developers that make all kinds of plug-ins for Adobe and other products. Occasionally Adobe will make a deal with one of the developers to buy their technology for one of their releases. This is standard practice in the computer industry. Sometimes the developers get bought out and the product disappears (Commotion was / is the best Rotoscoping app ever but the company was acquired and the product disappeared). It always gets down to a question of economics. If it's not profitable it will never happen.
Go to redgiantsoftware.com and look for the demo of Particular. While you could replicate the behavior in AE without additional effects, the project would be incredibly complex, require a vast knowledge of expressions and physics, and take you days or months to reproduce.
