Ankh — the Sign of Life
The looped cross that simply meant 'life' — held out by the gods to the king's lips.
Also: ankh · ʿnḫ · sign of life · key of life · crux ansata · looped cross · ankh symbol
The ankh is the famous looped-cross sign that wrote the Egyptian word for 'life.' In art, gods hold the ankh and extend it to the king's nose, giving him the breath of life. As a symbol it appears on temple walls, amulets, and objects throughout Egyptian history, standing for life itself and, by extension, vitality and well-being. Its original object-meaning is uncertain.
In short
The ankh — the hieroglyph and symbol meaning 'life' — one of the most pervasive Egyptian signs, held by gods and offered to the king as the breath and gift of life.
Where it’s found
Attested from the Early Dynastic Period; pervasive in temple and funerary art
How the idea developed across Egypt
Attested as a sign and motif from the Early Dynastic Period onward and ubiquitous thereafter; later adopted (as the crux ansata) in Coptic Christian Egypt — a reuse, marking the seam with the Christian stream.
The original object the ankh sign depicts is debated. Its Coptic-Christian reuse is later and marks the handoff to the Christian stream — note, don't annex.