There is some confusion out there about the difference between Typeface and Font.
What’s the difference?
Does it matter?
To answer 1: the definitions have changed somewhat since the evolution from mechanical printing to word processing, but they do still have different roles.
The Typeface is the design – how wide the letters are, how high the ascender is (e.g. on an ‘h’) or how low the descender is (e.g. on a ‘g’), and so on. A Font is a digital file that tells the computer one weight, width and style of a Typeface to display on screen or print off in a document.
A Typeface is made up of numerous Fonts. An example. Museo Slab is a typeface, part of the Museo family of typefaces by exlibris Font Foundry. Museo Slab 300 12px is a Font, and is specified within a digital file that tells the computer how to display or print the Typeface at that particular point.
Here’s a really good article that explains the difference in more depth.
To answer 2: it matters to pedants. And I am a pedant, so it matters – but only to a point. As Jason Santa Maria put it in On Web Typography (which is a wonderful book, and part of a wonderful series, A Book Apart, on website design), if a friend asks me what is a good font to use when they mean typeface,