1: The interface is a device designed and used to facilitate the relationship between systems.
An interface is a messenger.
Say we want to make a button and a lamp. The button when pressed must send an electric signal (message) to the lamp to turn it on. This electric signal is an interface, specially designed to work between objects that need to be remotely enabled.
To anyone who worked with computer interfaces before this seems to be obvious. Not so to the casual observer! In software, we use interfaces to connect one program (or different parts of a program) to another. In physical computing, interfaces are very important, which is why I chose the first tenant.
In the weather example for P5.Js, the function gotWeather() is an interface designed to help get the information from the weather API.
In my looking outwards, I wrote about claytronics. The team wrote a software interface between the 3D modeling program and the catons to shape the claytronic.