The term "Group VIII Metals" refers to the 3 by 3 block of elements boxed in red below, especially in older texts. link Note that they sit smack dab in the middle of the Periodic Table:
The 3 by 3 array is really three triads: first is the iron triad, comprising downwards iron, ruthenium, and osmium; the second triad is cobalt, rhodium, and iridium; the third triad is nickel, palladium, and platinum. So far in my series of posts about chemical elements, I've ignored the heavier metals, skimming sideways across the top of Group VIII, to get back to the right half of the Periodic Table. The metals below the blue line in the red box are called the platinum group metals: Ru, Rh, Pd, Os, Ir, and Pt. I will come back to them in due time. I know them the best of all the elements I've covered so far.
So why are they grouped together? First, they are usually found together (in nature), because they resemble each other chemically (though each element is of course distinct). Second, their electronegativities are similar to carbon's and to hydrogen's--this means that those main group elements tend to bond more covalently to the metals. Recall my point about the neutral ones--the covalent elements in the middle of a polarity continuum. Organotransition metal chemistry is largely (but not exclusively) the chemistry of those metals with hydrocarbons, hydrogen, and small organic molecules. The platinum group metals, especially rhodium, platinum, and palladium, are found for example in catalytic converters and fuel cells where they bring together disparate elements and catalyze their rearrangements.
One last thing. A lucky man discovered a process which still allows the modern day separation of the platinum group metals. He's the man who first gave metal wings.