The relationship between temperature and pressure in gases is described by Gay-Lussac's Law, which states that the pressure of a gas is directly proportional to its absolute temperature, provided the volume remains constant. As temperature increases, gas molecules gain energy and move more rapidly, causing increased collisions with container walls, thus raising pressure. Conversely, cooling a gas reduces molecular motion, leading to lower pressure. This relationship is fundamental to understanding gas behavior in various applications, such as in engines, weather systems, and engineering.