Using length on a string will return the number of letters, numbers, symbols, and whitespace characters.
Lists will return the number of items in the list.
Note that using length on an empty value — like "".length() — will return 0, while a list of empty values will still return the number of items.
Numbers will be formatted as strings before their length is calculated.
Dates, on the other hand, are seen as a single object, so will always return 1 when length is applied directly.