Typeface — A unified design for type characters, eg Helvetica. What most people mean when they say 'font'.
Leading, pronounced as in 'led' is the vertical space between lines of type.
Kerning is adjusting the horizontal spacing between a pair of letters.
Tracking is similar to kerning, which operates on pairs of letters, tracking is the process of optimizing the space between all of he characters in a word.
Serif — A font style with decorative strokes at the end of letters. Georgia, New York or Times New Roman are serif typefaces. Traditionally were considered to be more conservative, serious and suitable for long blocks of text (i.e. in books)
Sans-Serif — this is a typeface without serif details such as Helvetica, Futura or Verdana. Web typography tends toward sans-serif faces, previously associated with modernist design and headline text, as it's generally considered more legible on low-resolution devices such as television sets and computer monitors.

Learn more:
fontsmith.com — Fontsmith is a leading type design studio.
http://typographer.org/
Bringhurst "The elements of Typographic Style"