How it works...

If a struct provides a method called new that returns Self, the user of the struct will not configure or depend upon the members of the struct, as they are considered to be in an internal hidden state.

In other words, if you see a struct that has a new function, always use it to create the structure.
This has the nice effect of enabling you to change as many members of the struct as you want without the user noticing anything, as they are not supposed to look at them anyway.

The other reason to use this pattern is to guide the user to the correct way of instantiating a struct. If one has nothing but a big list of members that have to be filled with values, one might feel a bit lost. If one, however, has a method with only a few self-documenting parameters, it feels way more inviting.