A somersault: a full rotation of the body in the air, forward, backward or sideward, with no hand support.
“Salto” is the sport’s technical word for a somersault. Every salto can be described by:
Direction — forward, backward or sideward;
Rotations — a single, double or triple salto;
Twists — rotations around the body’s long axis, added on top;
Shape — tucked, piked or stretched (layout).
“Double back full”, for example, is a double backward salto with one full twist.
Saltos are central to the Codes of Points. On women’s floor, three of the four composition requirements involve saltos — one with at least a full twist, a double salto, and saltos both forward and backward — and an acro line must contain one. On men’s floor, a multiple salto is required, as the final skill for seniors. Values on women’s floor run from A for a single back salto to J for the Biles II, a triple-twisting double tuck.
Most tumbling skills are described by three things at once: the salto's direction, how many twists are added, and the body shape (tuck, pike or layout) it's performed in.
Tuck, pike and layout describe how the body is held during a salto: knees drawn in, legs straight and bent at the hips, or fully extended — with layout generally the hardest of the three.
A tumbling pass — an 'acro line' in the women's Code — is a run of linked acrobatic skills performed across the floor, usually corner to corner. Both Codes set rules on how many passes count, how they use the floor, and what the final one must be.
In women's floor, a tumbling pass of at least two directly connected flight elements, one of them a salto. Up to four acro lines count, and the last counting one is the dismount.