The piece of glass attached to your camera. There are different types of lenses.
A fixed focal length with no zoom. They can be 50mm, 28mm 85mm etc. They typically tend to have better results depending on manufacturer and have a fixed aperture as well.
A lens that zooms in and out. Lesser quality zooms will generally change aperture when zooming in and out depending on the range. Higher quality ones keep the same aperture throughout the zoom ranges. Once again, this depends on many different factors such as zoom range.
Lenses with a larger aperture (f1.4) are known as fast lenses. Lenses with a smaller aperture (over f4) are known as slow lenses.« Back to Glossary Index