The basic idea behind all string theories is that everything is fundamentally made up of strings of extremely small scale known as Planck length ( about 10-35 m) which vibrate at specific resonant frequencies. Any particle can be thought of as a tiny vibrating object, rather than as a point. These vibrations cause the strings to manifest themselves with various properies, because the string is forced through a Calabi-Yau manifold. This theory suggests that there are 11 dimensions that are 'compactified' and are so small relative to us that they appear as the four space-time dimensions that we know and love. String theory solves many conflicts between general relativity and quatum machanics, and serves as a plausible quantum theory of gravity if it is solved in a non-approximate form.
This is a Calabi-Yau manifold