Comment by igouy

fwiw

'what matters about an object is its protocol: the set of messages that it understands, and the way that it behaves in response to those messages. Nowadays, this is sometimes also referred to as the objectʼs interface. The key idea is that when we use an object, we focus on how it appears from the outside, and “abstract away from” its internal structure: more simply, that the internal structure of an object is hidden from all other objects. Thatʼs why I said “the set of messages that it understands,” and not “the set of methods that it implements.” In many languages they are the same, but I wanted to emphasise the external rather than the internal view.'

"Object-oriented programming: Some history, and challenges for the next fifty years" Andrew P. Black

https://doi.org/10.1016/j.ic.2013.08.002

So, a matter of emphasis?