The term abstraction as I understand it, is used in many different contexts, but has one essential meaning, namely that it refers to the “general properties of some class of objects that doesn’t rely on their details”. For example, abstraction in programming is e.g. interfaces that allow you to constrain a set of objects without specifying certain implementation details.
But in lambda calculus, I don’t see what “function abstraction” has to do with something like “independence of details”. It seems to me like “function application” or “argument substitution” makes more sense.
Am I missing something?
Ps. Note that I have only read an introductory chapter of a book on lambda calculus.