Typeface
A typeface is the overall design of a set of letterforms (e.g., Inter, Playfair Display). A font is a specific instance of a typeface at a specific weight, style, and size. The terms are often used interchangeably in modern usage.
In Practice
Typeface and font are often used interchangeably, but technically a typeface is the overall design family (Garamond, Helvetica, Inter) while a font is a specific weight and style within that family (Garamond Bold Italic, Helvetica Regular). In practice, most designers use "font" for both. Font Blend uses the term "font" throughout to match common usage.
Common Mistakes
The common mistake with most typographic terms is applying them without considering how they interact with other settings. Type is a system: changing kerning affects tracking, changing size affects leading, changing measure affects line-height. Test changes in context rather than in isolation.
Typeface vs font in daily work
The distinction is one of design versus container. A typeface is the drawing: the shapes that make Inter look like Inter. A font is the usable instance, a specific weight or style encoded as a file. Keeping the difference straight matters when you license one weight but assume the whole family, or when you pick a typeface and then realize the font you needed is a separate download.
Everyday speech has long since blended the two, and the site uses them loosely too. The practical consequence is information, not pedantry: know that a family can ship 18 files for nine weights in roman and italic, and that a variable font collapses that to one. When a spec says font, ask which weight and style. The font pages make the mapping visible by listing the weights each family actually ships.