Newbie question: what is DX10? Should I use it?

Just made a big leap of faith and moved from FS9 to FSX. 

I am not a happy camper yet as I have OOM problems, whcih I am educating myself on in the various forums. One thing I came across was "DX10". I have absolutely no clue about how computers work and what is under the hood of FSX, I just understand that there are settings menus and that moving the sliders to the left will improve performance.

So: what is DX10?

I have read that it may solve OOM problems, but also that it causes other problems.

If someone could give me a layman's answer to what DX10 is and what the pros and cons are of running it.

My setup:

FSX with SP2

Lots of add-on airports (FlyTampa, Aerosoft, FSDT, etc=

Add-on planes (PMDG, Level D, etc)

ORBX FTX Global

Not yet installed, but soon: FSGlobal mesh

Not yet ported over from FS9: plenty of AI, more than 1,000 bgls

Windows 8.1 

4th Generation i7

32GB RAM

GEFprce GTX 880M 4GB

(And by the way, if someone can point me to the ultimate FSX tweak and seetings guide, I'd appreciate. Like that I don't have to puzzle together everything from different threads and forums)

Thanks

Chris