Sometime it seems there are so many styles and options available for body jewelry now, it's hard to tell what to pick. Here are descriptions of some of the most common types of body jewelry and what makes each kind different.
At the most basic level, body jewelry is either based on a straight line (some type of barbell) or a circle (rings). There is even some jewelry that is right on the line between the two basic forms. Each has its own benefits and drawbacks. Many people pick what they think looks best and then switch to something that looks similar but functions better. There's no way to tell what will be best for you without a little bit of trial and error.
The most common type of ring jewelry worn in body piercings is the captured bead ring. The jewelry wire is bent almost into a circle, and the two ends pinch into an appropriately-sized bead, holding it in place. The diameter of the circle depends somewhat on the thickness of the wire and thicker gauges become larger rings out of necessity. This style of jewelry works for almost every single type of body piercing.
Capped with two beaded ends is the curved barbell. It's just a bit less of a circle than a captured bead ring and has independent ends, one of which is fixed closed and one which is threaded for jewelry removal. Curved barbells can also be so gently curved as to be less than 180 degrees of a circle. The end finish and opening methods remain consistent regardless of the degree of barbell curve.
Some variations of curved barbells have been used consistently enough that they have their own names now. A banana bar or an L-bar refer to two variations of curved barbell that are most often worn in navel piercings. The banana bar is a gentle curve with one smaller ball end and one larger, worn specifically top to bottom in the navel. An L-bar has an overall shape more like a hockey stick and is also worn top to bottom. A regular barbell is straight with ends that can be capped with small or large bead ends. Depending on the manufacturer, either the bar or the bead can be threaded.
To learn more about piercing, you might like Body Piercing: A Medical Dictionary, Bibliography, And Annotated Research Guide To Internet References by Icon Health Publications.
For body piercing aftercare, you might like Tattoo Goo Deluxe Tattoo & Piercing Care Kit or X-Pression & Blue Wave Piercing Aftercare Kit