Standard Deviation & Excepted Value

Can someone explain SD & EV to me "as if" I'm a 5 year old. I'm having a hard time understanding these to words.

How can I use them for a $2500 BR

I use KO

My spread is 1-12

AC Rules: S17, DAS

FW & MS Rules: S17, DAS, LS

I back-count and enter the game @ -1 hilo / +3 KO

LW

PS. I have BJA and I'm still confused.