As for the SSK, when you slip the stitch to the other needle, you do it by inserting the needle into the stitch as if you were going to knit it. Same with the second stitch. Then, when you slide them back onto the first needle, they have been twisted. Now you can knit them together. Sounds weird, I know. But it does look different than if you just knit them together. See a video here:

Here is a link that might be useful: SSK

The SSK produces a left leaning decrease while the K2tog produces a left leaning decrease. The SSK is usually used at the beginning of a right side row to produce the mirror image of the K2tog decrease worked on the left side at the end of the row in shaping a garment. You don't need to slip the two slipped stitches back to the left needle. Just leave them on the right needle and insert the left needle tip from left to right through the FRONT of the 2 slipped stitches and knit. Saves a step and makes it easier to remember.

It looks like you knit them off the right needle. Right?

Thanks everyone for the help. I decided to make a child's hat on two needles. There was just one row with the SSK in it. Now I have it down pat.

Whoops! In my previous post, I should've said that the K2tog produces a RIGHT leaning decrease. No wonder I get lost driving.