Introduced in the CSS3 specification, the rem behaves much like the em: it’s a relative unit of measurement, sizing text up or down from a baseline value. But the rem is sized relative to the root of your document—in other words, the value set on the body element.

This is a selection of single-character fonts. A single-character font is, literally, a font file that only contains glyphs for a single character. The single character in these font files is the ampersand.