Bike Parts Glossary
 

Handlebar: The tube you use to control the front wheel.

 

  • Mountain bike handlebars stretch perpendicularly across the front wheel--basically one straight bar. The clamp diameters (where the stem clamps on to the handlebar) on mountain handlebars are either 25.4mm or 31.8mm (referred to as "oversized").
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  • The tube of a road handlebar curves out perpendicularly to the front and drops down and under to allow for a more aerodynamic and aggressive riding stance. The clamp diameters on road handlebars are usually 26.0mm or 31.8mm.
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  • Triathalon (or aero) handlebars stretch out in front of the bike over the wheel and allow the rider to rest on his/her forearms while riding.

Handlebar tape: This is wrapped around the ends of road bike handlebars to provide cushioning and grip. It is often leather or cork and comes in a variety of colors, textures and thicknesses.
 
Excerpt from "Bike Parts Glossary"
By Jon Carter Davis - I suggest this place for Bike Parts