Hysteresis is a delay of the effect when the forces acting upon a body are changed (as if from viscosity or internal friction), or lagging in the values of resulting magnetization in a magnetic material (as iron) due to a changing magnetizing force.
The hysteresis error of a measuring instrument is defined as the maximum difference between the value detected by the transducer when a specific value of the input quantity is applied, by imposing increasing inputs, and the same value obtained by imposing decreasing inputs.
In other words, the hysteresis error is given by the maximum difference between the value measured in ascending direction and the respective value measured in a decreasing direction.
Hysteresis represents the history dependence of physical systems. If you push on something, it will yield: when you release, does it spring back completely? If it doesn’t, it is exhibiting hysteresis, in some broad sense.
The term is most commonly applied to magnetic materials: as the external field with the signal from the microphone is turned off, the little magnetic domains in the tape don’t return to their original configuration (by design, otherwise your record of the music would disappear!)
Hysteresis happens in lots of other systems: if you place a large force on your fork while cutting a tough piece of meat, it doesn’t always return to its original shape: the shape of the fork depends on its history.