The foundation is a text with attributes — a pair of a string and a map from string’s subranges to key-value dictionaries. Attributes express presentation (color, font, text decoration), but also semantics. A range of text can be designated as clickable. Or it can specify a custom keymap, which is only active when the cursor is on this range.

Unlike full HTML, the text is not nested, and logically is a 2 dimensional grid of characters. This makes text navigation universally applicable.

Unlike terminals there are multiple text buffers. You can have several apps running at the same time and displaying a text buffer each, or you could have a single app that owns multiple buffers.

Buffers are arranged in splits and tabs. Applications have limited control over the spatial arrangement of the buffers. It is the user who chooses which buffers are displayed in the foreground.