What are vectors and how do they work? Are they usable in Photoshop elements programs?
Vectors are lines or shapes described mathematically in software - we're usually talking Adobe Illustrator, Corel Draw etc. but we can use vector shapes and lines from inside PSE - generally the custom shapes and lines. Vector Shapes are created based on mathematical calculations rather than a specific number and pattern of pixels; this allows them to be resized without causing the image to become jagged, or pixelated. Every time a vector shape is changed in any way, PSE or CS redraws the image, filling in pixels as necessary; therefore, no quality is lost.
The Vector Shape tools include the Rectangle tool, the Rounded Rectangle tool, the Ellipse tool, the Polygon tool, the Line tool, and the Custom Shape tool. The Custom Shape tool lets you select a shape from a library of available shapes, such as arrows, check marks, footprints, and stars. You can download lots more, generally free, from the web. When the image is flattened, the vector shapes cease to be resizeable.