Raglan seams

I am a newbie and I have no idea what join raglan seams is can anyone help please, I am knitting a cardigan

What pattern are you using? Are you going top down or down up?

The raglan seam is the one between the body and the sleeve. It slopes up from the armpit to approx halfway along the collarbone.
Because it slopes, the top of both the sleeve and the body are shaped with decreases if the pattern is bottom up or increases if the pattern is top down. The shaping can be decorative or simple, and it can be sewn together or knitted in one piece.
I can recommend a new book by pompom magazine called Ready, Set, Raglan. with lots of beginners patterns .