Focal length: is the distance between where the lens focuses incoming light in the cameras digital sensor but it’s a lot easier to think of focal length as a magnification of the image so a higher focal length means higher magnification and a lower focal length means lower magnification
Aperture: there’s an opening in the back of the lens that opens and closes this is the aperture
Fixed Aperture: More expensive lenses have a fixed aperture that doesn’t change throughout the entire zoom range.
Fast/Slow Lenses: Fast lenses function better overall when working in low-light conditions, slow lenses do not.
Field of View (FoV): How much stuff can be seen in the frame. Also called Angle of view.
Perspective: Wide angle lenses make objects that are far away seem even further away, as well as smaller. Low angle lenses do the opposite.
Lens Distortion: Lenses that are wide enough tend to distort light to some degree. Be careful of this.
Lens Compression: Lenses that are much less wide tend to compress distance between two objects, the opposite of wide angle lenses.
Filters: There’s a number, usually, if not always, in millimeters, next to a circle with a slash through it. This is the diameter that you should memorize when using filters for a lens.
Macro: A photo that says “Macro” somewhere on the lens or camera are capable of getting really up close shots. Basically, it’s a magnifying glass.
Lens Mounts: Many different cameras and lenses have many different ways to attach. Be careful with this, and if you have to really try and force a lens onto a camera, you’re probably putting it on incorrectly!
Cinema Lenses: There are several noteworthy differences between photography lenses and cinema lenses.
Lens Breathing: The composition changes slightly when changing focus.
Cleaning Lenses: Be careful when cleaning lenses.
Lens Protection: Stay safe, kids. And clean this stuff, too, ’cause you probably spent a lot of money on one of these lenses.