%+ add 2 3
a rune is an operation named by two ASCII glyphs.
%+ is the call rune for a gate of two arguments — a gate is a function.
the (add 2 3) form is its irregular shorthand.
shown on one line here only to match that shorthand.
glossary
%+ calls a gate that takes two arguments.
%+(add 2 3) is 5.
irregular forms:
(gate a b) is %+(gate a b)
add sums two atoms.
(add 2 3) is 5.