Typography System
The organized use of typefaces, styles, spacing, and hierarchy to communicate clearly and consistently across a project.
In practice
A typography system is a fixed set of rules for type across a whole project: which typefaces, a scale of sizes, and the weights, line spacing and colors for each role, such as headings, body text, captions and buttons. It keeps hundreds of pages or screens consistent and speeds up work. An app might define five text styles and use only those, so every screen feels related.
Often confused with Typography
Typography is the overall craft of setting type; a typography system is the specific, documented set of type rules for one project.
Try this
Define four text styles, title, heading, body and caption, with sizes and weights, and apply them to one page.