The dwell of a point (in the Mandelbrot Set or a Julia Set) is the number of calculations (iterations) it takes, while calculating this point, before you end up a distance of at least two from the centre. A point is a member of the Mandelbrot Set or a Julia Set therefore has a dwell of infinity. In practice, Mandelbrot Explorer only calculates each point for a certain number of calculations (iterations); if at this stage you are still no more than two units from the centre, Mandelbrot Explorer decides that the point is a member of the relevant Fractal. This maximum number of calculations (iterations) is known as the Maximum Dwell. Unless you manually set a value for Maximum Dwell, Mandelbrot Explorer automatically uses an appropriate value.

For more information, see the Guides to the Mandelbrot Set and Julia Sets, available here.