In string theory, what are the fundemental properties of a string? Is the tension in the string a constant at all points on the string and the same in all strings? Is the string "labelled" with fields/spin/etc along its length? How about "velocity"? Is each 'bit' of the string labelled with a velocity, or is there only a world-sheet? (ie. can we distinquish between a worldsheet that is a cylinder, vs. a "rotating" cylinder with the same points in spacetime) Trying to find introductory papers, it looks like the strings have no properties besides tension ... which the action ends up being proportional to, so it is not even measureable. If the string really isn't "labelled" with any properties along its length, then it seems like a right handed neutrino and a left handed neutrino would have to have the same mass because the world sheet would look the same either way. What am I missing here?