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Differentiation - This is the process whereby materials of different densities separate from each other during igneous processes.  The Earth is a differentiated object - it has a dense metallic core, a less dense rocky mantle, and a low density rocky crust.

Figure from:  http://garage.physics.iastate.edu/astro120/lectlist.html - showing differentiation as a result of melting - dense material sinks, light material floats towards the surface.

Partial melting - This is an igneous process in which only part of the initial rock is melted.  Usually the portion that is melted (the partial melt) is more buoyant than the residual solid, and rises, resulting in differentiation.  The solidus is the minimum temperature at which the rock begins to melt.  Most terrestrial rocks begin to melt above 1000 degrees Celsius. The liquidus is the temperature at which the rock is entirely molten.

Fractional crystallization - This is an igneous process in which newly-formed crystals separate (usually sink) from the remaining magma during cooling, resulting in differentiation.  If solids accumulate during this process, they are called cumulates.  Any magma that is trapped between the cumulate crystals is called an intercumulus liquid.

Distribution coefficient or partition coefficient - This is a number that describes the tendency of an element to prefer a solid or liquid phase during an igneous process.

Exsolution - This is the process by which one mineral breaks down (exsolves) into separate minerals.  For example, Fe-Ni metal alloy exsolves as temperature decreases to form a low-Ni mineral and a high-Ni mineral.

Nebular condensation - This is the process whereby liquids or solids form (condense) from a cooling gas in the nebula, the mixture of gas and dust that existed as the solar system was forming.

Accretion - This is the process whereby smaller objects come together to form larger objects.  For example, all planets in the solar system are thought to have accreted from dust-sized objects.

Miller indices - Dodd refers to the orientation of features in crystals from iron meteorites by using Miller indices; an example is (111).  These numbers refer to the orientation of a plane relative to the atoms in a crystal structure.  You don't need to worry about these (unless you want to).

Figure from: http://www.keele.ac.uk/depts/ch/resources/xtal/miller2.html

Nickel diffusion gradients - If you are having difficulty understanding figure 7.3, you might want to check out this primer on nickel diffusion - http://www.eudil.fr/~hleroux/iron_meteorites/mineralogy.html

Polymorphs as pressure (depth) indicators - Dodd refers to the presence of graphite and tridymite as evidence that iron meteorites formed at reasonably low pressures.  Below are the relevant phase diagrams.

Figure from: http://www.unb.ca/courses/geol2142/LEC-31.html - Silica phase diagram,

Figure from: http://members.tm.net/lapointe/Z_Pinch.html - carbon phase diagram