Garamond is the name for any typeface based on the work of Claude Garamond, a 16-th century French punch-cutter. Basically, he was extremely influential in creating moveable type of “Roman” faces, the kinds we use. Before Garamond, most type was set in Blackletter, that old, fancy-looking style that many newspapers use for their names.
There are many versions of Garamond (the font, not the man) out there. Chances are you have one on your computer already. It might not look exactly like mine, but it should be close enough for this all to still apply.
Garamond is a very good, very classic, very serious typeface. It works well in books and for important texts.