This is something that puzzles me still to do this day. A lot of people use these two words, font and typface interchangeably, most likely to the point that Grammar Girl will have to comment on it soon. I was taught there is a difference and since have forgotten it, but perhaps if I write about it, the truth will stick eventually.
Typeface – A set of fonts in the same style. Or, in other words, a font family. Ex: Times New Roman, Helvetica, or Arial.
Font – A single kind of typeface. Ex: Times New Roman in 10 point size is a font, and Times New Roman in 14 point size is also a font. Times New Roman in Bold is also a font. (Basically designating a specific type inside of a typeface is a font.)
So that clears the air a bit. So, if you are looking at typography in a magazine, or during a presentation and happen to like it, you could ask “what font is that sentance set to?”, or if you think the whole page of differing point sizes is in the same family, “What typeface are you using for this presentation?”. It seems instead of using font and typeface interchangeably and being wrong, you might be able to use the phrase font-family and the word typeface interchangeably.
Brilliant!