Development is Progressive and involves changes in a cell's biochemistry, structure and function. A cell's prospective fate is defined as what it would normally become in an embryo. On the way to becoming different from other cell types, cells in the embryo progress from being totipotent, to being specified, to being determined, to being differentiated.
Cells becomes determined at different times.
Determination is defined as the process of becoming committed to a particular developmental fate. The concept implies a stable alteration in the internal state of a cell. Specification is defined as being somewhere on the path to being determined. To find out where cells are along this pathway, experiments are required. Determined cells continue to develop in accord with their prospective fate even when placed into a different region of the embryo.