Ipads are a great technological advance, but there are extras that make them run more smoother and an ipad pen is one of them essential extras. The stylus pen is one that has been chatted up online as an ultra crap pen, especially the cheaper ones, whilst the Pogo Sketch is considered a great ipad pen, because all you really need is the ability to draw on the screen without leaving finger prints on your ipad screen.
An ipad pen helps you draw more precise line work in your digital illustrations and there are a great selection of ipad pens available and these pens are either ones you plug in or are wireless, I prefer the wireless pens as you don't have the wire getting in the way all the time when you are drawing on your ipad screen.
What you need is a pen that acts like what a finger would do when you touch the screen, plastic pens won't do the job very well and so you may need to pay a few dollars more for your ipad pens that seem to act like a finger tip would when drawing, so in this respect you may need the Pogo sketch or The Pogo Stylus as these are good quality ipad pens. There maybe other better pens that comes out every now and then, so you may want to sop around or enquire online a bit as technology does change a lot.
Drawing with your finger is okay on the ipad, but an ipad pen is way better as it focuses the surface area much better and draws just like on a graphics tablet. Shop online for the best ipad pens as they aren't that expensive.