What's the difference between the left curly brace and the right curly brace?

Open braces{, as stated in the documentation shown in your question, is a primitive function, but close braces is just a syntax marker. The closing brace } has no independent function/documentation because it only exists to define the boundaries of the opening brace.

You can actually call { like a function (it is a function after all):

2+3; 4+5
#> [1] 5
#> [1] 9
{2+3; 4+5}
#> [1] 9
{(2+3, 4+5)
#> [1] 9

^{Created on 2026-06-24 with reprex v2.1.1}

look this { is a function. } is just punctuation.

• { groups expressions and returns the last one.

• } doesn't do anything — it just tells R where the block ends.

That's why ?{ works and ?} doesn't.

It's like asking for the difference between ( and ) — one opens, the other closes. Only the opener is the function.

Hope that clears it up."