Let's toss a fair coin. If it's heads, I'll give you $2. If it's tails, you give me $1. What's the EV of a single toss? $0.50. Why? That's the expected value you'll get on average.

Hint: After two tosses, you'll average being up $1, so that means after one toss, $0.50.

The extension to poker is pretty straight-forward.

I don't have MSN but that's my best shot at simple EV explanation.