Anyone help me understand what SDK is?

Hi,

I see people talking about SDK a lot in regards to Reason being " brought up to date" with other audio software producers. I keep meaning to have a look around and do some reading on it, but haven' t found time yet.Anyone on here up for breaking it down for me, and maybe explaining it in terms of reason devices and VSTs (as I notice that is where the comparison is made.) What are the major pro' s to the updated SDK thing?

Please help.

I didn' t find the right solution from the Internet.

References:-

https://forum.reasontalk.com/viewtopic.php?t=7491521
Video content production agency

Thanks!