Ligatures: Ligatures are when two characters or letters are connected by one small characteristic. Many fonts have this as to avoid the awkward space caused by letters that have tails or are much wider than normal letters. To they become connected to have a more clean look. Common letters that use ligatures are "f" and "i". or "v" and "w". Rockwell does not have ligatures, but an example is Adobe Garamond Pro.
Foot marks and inch marks vs. Apostrophes and quote marks: Footmarks are used in measurements, such as when abbreviating for "feet". Apostrophes are just a character used for proper grammar. The same goes for quote marks and inch marks, but inch marks are used to abbreviate inches.
Hyphen, En Dash, and Em Dash: Hyphens are used in proper grammar to either separate one word, or to combine two words. En Dashes and Em Dashes are the same thing but just in different sizes, the En Dash is originally suppose to be the same length as the "n" in that font, and the Em Dash is suppose to be equal to the "m" length. The hyphen then being the smallest of the three.