It refers to the act of using the map method with an Option type in Rust.

In Rust, an Option is an enum type that represents the presence or absence of a value. It has two variants: Some(value) and None. The Some variant contains a value of any type, while the None variant represents the absence of a value.

The map method is to transform the value inside an Option while preserving the Option type. When you call map on an Option value, it applies a closure to the inner value.

In Rust, a closure is a function-like value that can be defined inline without a name. Closures are defined using the |...| ... syntax and are often used to pass behavior as an argument to functions.

Here’s an example:

Or you can use a function called square instead as the argument:

Here’s another example of using the map method with an Option type: