A CSS distance measurement is a number immediately followed by a length unit (px, em, pc, in, …)
CSS supports a number of length measurements units. They are absolute or relative.
Traits are a way of describing a 'contract' that a
struct must implement. Traits typically define method signatures but can also provide implementations based on other methods of the trait, providing the trait bounds allow for this.
For those familiar with object oriented programming, traits can be thought of as interfaces with some subtle differences.