What does single quotes do? The first item in the bullet point list in section 15.1 in the Nix reference guide says

> Since ${ and '' have special meaning in indented strings, you need a way to quote them. $ [...] can be escaped by prefixing it with ', i.e., '''. 

but nothing about what single quotes otherwise do. Or are they only for escaping in string?

I'm trying to figure out what they do in the context of running the following command (taken from the Nix reference guide)

`$ nix-shell '<nixpkgs>' -A pan`.