Refers to the design of a set of characters for printing or display; a technical term in typography.
This typeface is easy to read.
フォント is a more common, general term for a font, often used in digital contexts, while 活字書体 is a technical term specifically for typeface design, historically associated with metal type.
Compound of 活字 (movable type) and 書体 (script style, typeface). The term is transparently derived from its components.