What does the -> symbol mean?

<<It's actually a binary (one-argument, infix) method, like +, =, or ==;
it's the - and > characters put together rather than being a
specialized glyph like the left arrow was. It creates an Association,
which is a key-value pair used in things like Dictionaries.

If I remember correctly, any characters which can be used for binary
methods can be strung together to make other binary methods -
sometimes you'll see these turn up in specialized contexts. For
example, there's also ==>, on Booleans, for implication ("a implies b").

Ben Schroeder>>