When I see a 2GB + 8GB Android TV advertised, what does that mean?

I assume that since the 2GB is advertised as DDR3 it is used for the executable code at runtime, and that it may also be used for streaming content store / queue.

Is it true that the 8GB is flash, and is used to store the OS, the apps and the add-ons? Is it also used to store incoming streamed data?

Finally, in practice, how often does 2GB of DDR3 have a performance edge (or capability edge if executables are large) over 1GB?

Thanks for the answers to the general questions.