# 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?

• I think my confusion is around the dimensionality. I'm going to guess a particle's one dimensional trajectory corresponds to proper time. If so, what are the two dimensions we use for strings? I will guess again and suppose they are $\sigma$ and $\tau$. But what does that mean? I thought proper time was an affine parameterization of the curve distance traveled along a curve on on a spacetime manifold. What would the $\sigma$ be parameterizing? – Stan Shunpike Feb 18 '15 at 1:09
• @StanShunpike: The $\sigma$ is the spatial coordinate on the string, the $\tau$ is the time variable, i.e. the $\sigma$ is where on the string you look and the $\tau$ is when. – ACuriousMind Feb 18 '15 at 1:12
• But for strings does $\tau$ signify proper time or regular time? – Stan Shunpike Feb 18 '15 at 1:19