Consider the air surrounding us. The air is composed of many molecules. Consider some considerable volume of air, where there is same temperature everywhere. We cannot still say that all molecules of air in the considered volume travel at the same speed. Some molecules move fast, some move at moderate speed, some move slowly while some do not move at all.

Maxwell-Boltzmann distribution  shows how the speeds of molecules are distributed for an ideal gas. The Maxwell-Boltzmann distribution is represented in the form of a graph.

The graph represents the number of molecules on the Y-axis and speed along the X-axis.

The peak of the graph shows that more gas molecules are moving with the respective speed.

At higher temperature, the peak of the graph shifts to the right as the average molecular speed of the gas will increase. The height of the graph decreases as the peak of the graph shifts, in order to maintain the same total area under the curve.