Knitting needles are those indispensible tools of the knitting trade that seem so simple and yet are available in an immense variety. Many people remember the long skinny metal sticks that their Grandmothers used and the sound of the click click click, stitch by stitch. Today, needles are found in just about any material. The most popular ones are:
Metal: smooth, good for quick stitches, can be more difficult for slicker yarns.
Wood: Warm to work with, more mailable will flex while working, better for slick yarn and tighter stitches.
Plastic: Light, smooth, flexible. Can become very warm while using.
Bamboo: Has a lot of the same qualities as wood needles but are lighter. They are also more abt to breaking (as I have broken my share of cheap ones).
If you are just starting out, try different needles to see what is most comfortable. As with everything, different people like different materials. My favorites of the moment are my Knitpicks Harmony needles and the Lantern Moon Sox Sticks. I do go through phases where I prefer to use metal needles.