FM6: Apex is essentially the same game Xbox One players have been enjoying since September 2015. But DirectX 12 support and 4K resolution, if your PC has the internals to handle it, will make an already pretty game prettier. The beta will be an evolving process, according to Turn 10, with support for additional machine configurations, wheel setups, and other features coming online as things advance.
As our friends at Engadget explained, FM6: Apex is an exciting development, but it's best to think of more as a proving ground for Turn 10 than anything. For one, it's free. But that also means you aren't going to get a lot of cars or tracks – there are 63 vehicles and six locations to race. According to our gadgety friends, a successful run with Apex could lead the next Forza title to debut on both consoles and PCs at roughly the same time.
The open beta for Apex will run through the summer. You can hop over to the Forza website for more details, including a full range of tech specs (the "Ideal" setup will probably make you choke).