What Is Font?
A font is a specific instance of a typeface — one weight, width, and style at a given size. "Arial Bold 14pt" is a font; "Arial" is the typeface. In digital design a font is also the file (TTF, OTF, WOFF2) that contains the character outlines your software renders.
In metal type, a font was a physical drawer of sorts — every piece of type for one size and style of a typeface. Buying "more font" meant buying more lead. That one-size-one-style meaning is why "font" and "typeface" were once clearly different things.
Digital fonts collapsed much of that distinction: a single OpenType file can scale to any size and often bundles multiple weights. When you download a font from FontBoxDL you usually get one or more files covering a whole family.