What are the concepts of math required as a prerequisite to understand Knot Theory?
I'd like to be able to make a humble beginning by being able to mathematically define knots and the non-rigid transformations one can make with knots made of ropes, in real life.
You don't need to have an extensive background to understand the fundamental ideas of Knot Theory. I would suggest reading The Knot Book: An Elementary Introduction to the Mathematical Theory of Knots by Colin C. Adams. It's an excellent introduction to the subject and it will give you a starting point for further studies.
From the Preface: