A "wavepacket" is simply a single composite wave made up of two
or more individual waves combining with each other in a
consistent fashion over time. Wavepackets are an important
concept in quantum mechanics. For an electron, atom, molecule,
or any other quantum system, an individual quantum state can be
represented as a stationary or "standing" wave whose points of
maximum disturbance (peaks and valleys) and points of minimum
disturbance (known as nodes) stay fixed. When a group of
individual quantum states (right) add together, they combine to
form a wavepacket (left). Under certain conditions, the
resulting wavepacket can consist of a single peak (as depicted
on the left)--causing the quantum system to act as a particle in
a well-defined state, instead of the more customary quantum wave
spread out in space.