How is a string in string theory different from a harmonic oscillator or a point? I am reading String Theory and M-Theory: A Modern Introduction by Becker, Becker and Schwartz. I've tried to read this book before but not succeeded because I didn't know enough math or physics. This time, I feel like I am following it much better but I still don't understand what a string is. 
All the concepts I've read so far  either to fall into the category of stuff that could be described by a harmonic oscillator or the category of stuff that could be described by a point. But what does a string offer that these concepts don't?  I still don't really understand what a string it is and I think that's partly because I don't see what the idea offers that's new. 
My Question:
How is a string in string theory different from a harmonic oscillator or a point?  
 A: A string is a one-dimensional object, and not a zero-dimensional like a point.
This means that the object traced out by it following its trajectory is a two-dimensional surface, the worldsheet, while particles - points - trace out one-dimensional objects, the worldlines.
Much of the difference between string theory and theories with particles as the fundamental objects arises from this conceptually simple difference - in particular, the worldsheets of two strings merging and unmerging again are also just smooth 2D surfaces, while the corresponding object in particle theories - a Feynman diagram - has these ugly vertices instead of being smooth.
Also, 2D "world-objects" are special in that the natural action functional on them - the Nambu-Goto action or the related Polyakov action - is conformally invariant (and only on them - the Polyakov action is Weyl invariant only in 2D), leading to a much more constrained theory compared to a generic QFT, because it forces the theory to have the Virasoro algebra as an infinite-dimensional symmetry.
