Flared is a real-time lens flare generator that works directly in the viewport of Blender, using Eevee engine.
So you can have a direct preview of the final result without the need to use the compositor. It's not screen space-based, so it works also when light sources move out of the screen.
It takes advantage of procedural materials, so it's resolution-independent. It's easy to use and customize and can help you to add cinematic looks to your 3D scenes or give more drama to your real video footages.
Flared it's not a physical simulation of the light path through the lens, it's a powerful artistic instrument.
Here is an example: in this short CGI video the Sun is made with Flared:
Here is another example of how it works:
Here is a generic video that shows some features of Flared (as it's an old video, maybe it's talking about old blender versions, don't care about it).
Flared has been on sale for 9 months. During this period, we had time to test and improve it. Here is the full Youtube Playlist with information and tutorials (note: some videos are obsolete, we have removed the anti-piracy system, so now you can work with Flared without any restrictions).
You can find more details on the official website too.