Statistical mechanics is a branch of physics that studies how things like atoms, molecules, and particles behave on a large scale. It uses mathematics and statistics to predict how these particles move, interact, and behave. For example, statistical mechanics can be used to figure out the average temperature of a gas or the behavior of a gas in a container. By looking at the average behavior of many particles, statistical mechanics can help us understand the behavior of bigger things, like the weather or the ocean.