What is M-theory and Parallel universes ?
These are two completely different things. Parallel universes are a way to interpret/explain certain philosophical problems with Quantum Mechanics. M-theory is… well, a long story by now. We are used to thinking of fundamental particles like electrons and quarks as point-like 0-dimensional objects. A generalization of this are strings, which 1-dimensional objects and have a length, typically so small to the length scales that we can measure, so that these strings are so small that they practically look like point particles. However, the fact that they have a length, means that the can vibrate, like the string of a violin. The basic idea is that each different vibration mode, say each not, corresponds to a different fundamental particle. When the theoretical physicists started running with this idea, they came up with basically five different versions, of this string theory. The differences lie in the way the extra string dimension is added to our seemingly 4-dimensional space time an
