So basically you're making a triangle. As you do the decreases on each side, one decrease slants to the left and the other slants tot he right. You'll end up with these funny looking triangle things. The shoulders form the other side of the trianlge and when you seam them together they make that slanty looking thing like in that picture Katykoolkat sent.
I have a top down pattern for raglan sleeves. What is, you make sort of fake ragland "seam" by knitting a stich different from the pattern and make that stich slant like a ragland sleeve would. Then when you get to where the armpits would be you pich it together to make an armhole and continue knitting down. Then when yer done you go back and pick up stiches for the arm and knit the sleeves. Hmmm.... That makes no sense. Maybe I should take some pictures of sweaters so you know what I mean.