What the sign label means
The third sidereal sign. When Gemini rises, the entire Gemini sign is house one in a whole-sign chart.
A body is listed in Gemini when its normalized sidereal longitude falls from 60°00′ up to—but not including—90°00′. The exact degree within the sign remains important, particularly near either edge.
Sign is not the same as house
The sign is a fixed part of the 360° circle. In a whole-sign chart, the house number depends on the ascendant: the rising sign is house one, and the following signs are numbered in order. Gemini can therefore be a different house in different birth charts.
Element and mode are traditional classification labels. They do not, on their own, establish a personality or predict an event.