...now vee may perhaps to begin?

You have to start somewhere - you can start with a definition, I suppose, and most of us start with the definition offered by google. It does not yield much! I demonstrate this to students in my Modern Fiction course, who are supposed to find a definition for "modernity" - and are being told that "modernity relates to being modern," which is not helpful, as we then all see.
But yes, "interdisciplinary" relates to multiple branches of knowledge, or disciplines - we may perhaps already wonder how knowledge is organized. And why! Education provides a lot of examples of such organization: courses, exams, text books, majors and minors, standards. Organization helps render an unbelievable amount of information manageable - we feel like we have mastered some part of a whole when we have read a chapter, passed an exam, earned a degree. Knowledge is framed, focused. On the other hand, those frames are somewhat arbitrary - and sometimes connections and relationships are cut off, in order to simplify what we look at.
Interdisciplinary studies allows for some of those connections and relationships to be added back in, to allow us to look at different contexts and intersections.